which presentation is good for normal delivery

Appointments at Mayo Clinic

• Pregnancy week by week
• Fetal presentation before birth

The way a baby is positioned in the uterus just before birth can have a big effect on labor and delivery. This positioning is called fetal presentation.

Babies twist, stretch and tumble quite a bit during pregnancy. Before labor starts, however, they usually come to rest in a way that allows them to be delivered through the birth canal headfirst. This position is called cephalic presentation. But there are other ways a baby may settle just before labor begins.

Following are some of the possible ways a baby may be positioned at the end of pregnancy.

Head down, face down

When a baby is head down, face down, the medical term for it is the cephalic occiput anterior position. This the most common position for a baby to be born in. With the face down and turned slightly to the side, the smallest part of the baby's head leads the way through the birth canal. It is the easiest way for a baby to be born.

Head down, face up

When a baby is head down, face up, the medical term for it is the cephalic occiput posterior position. In this position, it might be harder for a baby's head to go under the pubic bone during delivery. That can make labor take longer.

Most babies who begin labor in this position eventually turn to be face down. If that doesn't happen, and the second stage of labor is taking a long time, a member of the health care team may reach through the vagina to help the baby turn. This is called manual rotation.

In some cases, a baby can be born in the head-down, face-up position. Use of forceps or a vacuum device to help with delivery is more common when a baby is in this position than in the head-down, face-down position. In some cases, a C-section delivery may be needed.

Frank breech

When a baby's feet or buttocks are in place to come out first during birth, it's called a breech presentation. This happens in about 3% to 4% of babies close to the time of birth. The baby shown below is in a frank breech presentation. That's when the knees aren't bent, and the feet are close to the baby's head. This is the most common type of breech presentation.

If you are more than 36 weeks into your pregnancy and your baby is in a frank breech presentation, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. It involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a breech position, talk with a member of your health care team about the choices you have for delivery. Most babies in a frank breech position are born by planned C-section.

Complete and incomplete breech

A complete breech presentation, as shown below, is when the baby has both knees bent and both legs pulled close to the body. In an incomplete breech, one or both of the legs are not pulled close to the body, and one or both of the feet or knees are below the baby's buttocks. If a baby is in either of these positions, you might feel kicking in the lower part of your belly.

If you are more than 36 weeks into your pregnancy and your baby is in a complete or incomplete breech presentation, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. It involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a breech position, talk with a member of your health care team about the choices you have for delivery. Many babies in a complete or incomplete breech position are born by planned C-section.

When a baby is sideways — lying horizontal across the uterus, rather than vertical — it's called a transverse lie. In this position, the baby's back might be:

• Down, with the back facing the birth canal.
• Sideways, with one shoulder pointing toward the birth canal.
• Up, with the hands and feet facing the birth canal.

Although many babies are sideways early in pregnancy, few stay this way when labor begins.

If your baby is in a transverse lie during week 37 of your pregnancy, your health care professional may try to move the baby into a head-down position. This is done using a procedure called external cephalic version. External cephalic version involves one or two members of your health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

If the procedure isn't successful, or if the baby moves back into a transverse lie, talk with a member of your health care team about the choices you have for delivery. Many babies who are in a transverse lie are born by C-section.

If you're pregnant with twins and only the twin that's lower in the uterus is head down, as shown below, your health care provider may first deliver that baby vaginally.

Then, in some cases, your health care team may suggest delivering the second twin in the breech position. Or they may try to move the second twin into a head-down position. This is done using a procedure called external cephalic version. External cephalic version involves one or two members of the health care team putting pressure on your belly with their hands to get the baby to roll into a head-down position.

Your health care team may suggest delivery by C-section for the second twin if:

• An attempt to deliver the baby in the breech position is not successful.
• You do not want to try to have the baby delivered vaginally in the breech position.
• An attempt to move the baby into a head-down position is not successful.
• You do not want to try to move the baby to a head-down position.

In some cases, your health care team may advise that you have both twins delivered by C-section. That might happen if the lower twin is not head down, the second twin has low or high birth weight as compared to the first twin, or if preterm labor starts.

• Landon MB, et al., eds. Normal labor and delivery. In: Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Elsevier; 2021. https://www.clinicalkey.com. Accessed May 19, 2023.
• Holcroft Argani C, et al. Occiput posterior position. https://www.updtodate.com/contents/search. Accessed May 19, 2023.
• Frequently asked questions: If your baby is breech. American College of Obstetricians and Gynecologists https://www.acog.org/womens-health/faqs/if-your-baby-is-breech. Accessed May 22, 2023.
• Hofmeyr GJ. Overview of breech presentation. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
• Strauss RA, et al. Transverse fetal lie. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
• Chasen ST, et al. Twin pregnancy: Labor and delivery. https://www.updtodate.com/contents/search. Accessed May 22, 2023.
• Cohen R, et al. Is vaginal delivery of a breech second twin safe? A comparison between delivery of vertex and non-vertex second twins. The Journal of Maternal-Fetal & Neonatal Medicine. 2021; doi:10.1080/14767058.2021.2005569.
• Marnach ML (expert opinion). Mayo Clinic. May 31, 2023.

Products and Services

• A Book: Obstetricks
• A Book: Mayo Clinic Guide to a Healthy Pregnancy
• 3rd trimester pregnancy
• Fetal development: The 3rd trimester
• Overdue pregnancy
• Pregnancy due date calculator
• Prenatal care: 3rd trimester

Mayo Clinic does not endorse companies or products. Advertising revenue supports our not-for-profit mission.

• Opportunities

Mayo Clinic Press

Check out these best-sellers and special offers on books and newsletters from Mayo Clinic Press .

• Mayo Clinic on Incontinence - Mayo Clinic Press Mayo Clinic on Incontinence
• The Essential Diabetes Book - Mayo Clinic Press The Essential Diabetes Book
• Mayo Clinic on Hearing and Balance - Mayo Clinic Press Mayo Clinic on Hearing and Balance
• FREE Mayo Clinic Diet Assessment - Mayo Clinic Press FREE Mayo Clinic Diet Assessment
• Mayo Clinic Health Letter - FREE book - Mayo Clinic Press Mayo Clinic Health Letter - FREE book
• Healthy Lifestyle

Your gift holds great power – donate today!

Make your tax-deductible gift and be a part of the cutting-edge research and care that's changing medicine.

Fetal Presentation, Position, and Lie (Including Breech Presentation)

• Variations in Fetal Position and Presentation |

During pregnancy, the fetus can be positioned in many different ways inside the mother's uterus. The fetus may be head up or down or facing the mother's back or front. At first, the fetus can move around easily or shift position as the mother moves. Toward the end of the pregnancy the fetus is larger, has less room to move, and stays in one position. How the fetus is positioned has an important effect on delivery and, for certain positions, a cesarean delivery is necessary. There are medical terms that describe precisely how the fetus is positioned, and identifying the fetal position helps doctors to anticipate potential difficulties during labor and delivery.

Presentation refers to the part of the fetus’s body that leads the way out through the birth canal (called the presenting part). Usually, the head leads the way, but sometimes the buttocks (breech presentation), shoulder, or face leads the way.

Position refers to whether the fetus is facing backward (occiput anterior) or forward (occiput posterior). The occiput is a bone at the back of the baby's head. Therefore, facing backward is called occiput anterior (facing the mother’s back and facing down when the mother lies on her back). Facing forward is called occiput posterior (facing toward the mother's pubic bone and facing up when the mother lies on her back).

Lie refers to the angle of the fetus in relation to the mother and the uterus. Up-and-down (with the baby's spine parallel to mother's spine, called longitudinal) is normal, but sometimes the lie is sideways (transverse) or at an angle (oblique).

For these aspects of fetal positioning, the combination that is the most common, safest, and easiest for the mother to deliver is the following:

Head first (called vertex or cephalic presentation)

Facing backward (occiput anterior position)

Spine parallel to mother's spine (longitudinal lie)

Neck bent forward with chin tucked

Arms folded across the chest

If the fetus is in a different position, lie, or presentation, labor may be more difficult, and a normal vaginal delivery may not be possible.

Variations in fetal presentation, position, or lie may occur when

The fetus is too large for the mother's pelvis (fetopelvic disproportion).

The uterus is abnormally shaped or contains growths such as fibroids .

The fetus has a birth defect .

There is more than one fetus (multiple gestation).

Position and Presentation of the Fetus

Variations in fetal position and presentation.

Some variations in position and presentation that make delivery difficult occur frequently.

Occiput posterior position

In occiput posterior position (sometimes called sunny-side up), the fetus is head first (vertex presentation) but is facing forward (toward the mother's pubic bone—that is, facing up when the mother lies on her back). This is a very common position that is not abnormal, but it makes delivery more difficult than when the fetus is in the occiput anterior position (facing toward the mother's spine—that is facing down when the mother lies on her back).

When a fetus faces up, the neck is often straightened rather than bent,which requires more room for the head to pass through the birth canal. Delivery assisted by a vacuum device or forceps or cesarean delivery may be necessary.

Breech presentation

In breech presentation, the baby's buttocks or sometimes the feet are positioned to deliver first (before the head).

When delivered vaginally, babies that present buttocks first are more at risk of injury or even death than those that present head first.

The reason for the risks to babies in breech presentation is that the baby's hips and buttocks are not as wide as the head. Therefore, when the hips and buttocks pass through the cervix first, the passageway may not be wide enough for the head to pass through. In addition, when the head follows the buttocks, the neck may be bent slightly backwards. The neck being bent backward increases the width required for delivery as compared to when the head is angled forward with the chin tucked, which is the position that is easiest for delivery. Thus, the baby’s body may be delivered and then the head may get caught and not be able to pass through the birth canal. When the baby’s head is caught, this puts pressure on the umbilical cord in the birth canal, so that very little oxygen can reach the baby. Brain damage due to lack of oxygen is more common among breech babies than among those presenting head first.

In a first delivery, these problems may occur more frequently because a woman’s tissues have not been stretched by previous deliveries. Because of risk of injury or even death to the baby, cesarean delivery is preferred when the fetus is in breech presentation, unless the doctor is very experienced with and skilled at delivering breech babies or there is not an adequate facility or equipment to safely perform a cesarean delivery.

Breech presentation is more likely to occur in the following circumstances:

Labor starts too soon (preterm labor).

The uterus is abnormally shaped or contains abnormal growths such as fibroids .

Other presentations

In face presentation, the baby's neck arches back so that the face presents first rather than the top of the head.

In brow presentation, the neck is moderately arched so that the brow presents first.

Usually, fetuses do not stay in a face or brow presentation. These presentations often change to a vertex (top of the head) presentation before or during labor. If they do not, a cesarean delivery is usually recommended.

In transverse lie, the fetus lies horizontally across the birth canal and presents shoulder first. A cesarean delivery is done, unless the fetus is the second in a set of twins. In such a case, the fetus may be turned to be delivered through the vagina.

• Cookie Preferences

Copyright © 2024 Merck & Co., Inc., Rahway, NJ, USA and its affiliates. All rights reserved.

An official website of the United States government

The .gov means it's official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you're on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings
• Browse Titles

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

StatPearls [Internet].

Delivery, face and brow presentation.

Julija Makajeva ; Mohsina Ashraf .

Affiliations

Last Update: January 9, 2023 .

• Continuing Education Activity

Face and brow presentation is a malpresentation during labor when the presenting part is either the face or, in the case of brow presentation, it is the area between the orbital ridge and the anterior fontanelle. This activity reviews the evaluation and management of these two presentations and explains the role of the interprofessional team in managing delivery safely for both the mother and the baby.

• Describe the mechanism of labor in the face and brow presentation.
• Summarize potential maternal and fetal complications during the face and brow presentations.
• Review different management approaches for the face and brow presentation.
• Outline some interprofessional strategies that will improve patient outcomes in delivery cases with face and brow presentation issues.
• Introduction

The term presentation describes the leading part of the fetus or the anatomical structure closest to the maternal pelvic inlet during labor. The presentation can roughly be divided into the following classifications: cephalic, breech, shoulder, and compound. Cephalic presentation is the most common and can be further subclassified as vertex, sinciput, brow, face, and chin. The most common presentation in term labor is the vertex, where the fetal neck is flexed to the chin, minimizing the head circumference.

Face presentation – an abnormal form of cephalic presentation where the presenting part is mentum. This typically occurs because of hyperextension of the neck and the occiput touching the fetal back. Incidence of face presentation is rare, accounting for approximately 1 in 600 of all presentations. [1] [2] [3]

In brow presentation, the neck is not extended as much as in face presentation, and the leading part is the area between the anterior fontanelle and the orbital ridges. Brow presentation is considered the rarest of all malpresentation with a prevalence of 1 in 500 to 1 in 4000 deliveries. [3]

Both face and brow presentations occur due to extension of the fetal neck instead of flexion; therefore, conditions that would lead to hyperextension or prevent flexion of the fetal neck can all contribute to face or brow presentation. These risk factors may be related to either the mother or the fetus. Maternal risk factors are preterm delivery, contracted maternal pelvis, platypelloid pelvis, multiparity, previous cesarean section, black race. Fetal risk factors include anencephaly, multiple loops of cord around the neck, masses of the neck, macrosomia, polyhydramnios. [2] [4] [5]

These malpresentations are usually diagnosed during the second stage of labor when performing a digital examination. It is possible to palpate orbital ridges, nose, malar eminences, mentum, mouth, gums, and chin in face presentation. Based on the position of the chin, face presentation can be further divided into mentum anterior, posterior, or transverse. In brow presentation, anterior fontanelle and face can be palpated except for the mouth and the chin. Brow presentation can then be further described based on the position of the anterior fontanelle as frontal anterior, posterior, or transverse.

Diagnosing the exact presentation can be challenging, and face presentation may be misdiagnosed as frank breech. To avoid any confusion, a bedside ultrasound scan can be performed. [6]  The ultrasound imaging can show a reduced angle between the occiput and the spine or, the chin is separated from the chest. However, ultrasound does not provide much predicting value in the outcome of the labor. [7]

• Anatomy and Physiology

Before discussing the mechanism of labor in the face or brow presentation, it is crucial to highlight some anatomical landmarks and their measurements. 

Planes and Diameters of the Pelvis

The three most important planes in the female pelvis are the pelvic inlet, mid pelvis, and pelvic outlet. 

Four diameters can describe the pelvic inlet: anteroposterior, transverse, and two obliques. Furthermore, based on the different landmarks on the pelvic inlet, there are three different anteroposterior diameters, named conjugates: true conjugate, obstetrical conjugate, and diagonal conjugate. Only the latter can be measured directly during the obstetric examination. The shortest of these three diameters is obstetrical conjugate, which measures approximately 10.5 cm and is a distance between the sacral promontory and 1 cm below the upper border of the symphysis pubis. This measurement is clinically significant as the fetal head must pass through this diameter during the engagement phase. The transverse diameter measures about 13.5cm and is the widest distance between the innominate line on both sides. 

The shortest distance in the mid pelvis is the interspinous diameter and usually is only about 10 cm. 

Fetal Skull Diameters

There are six distinguished longitudinal fetal skull diameters:

• Suboccipito-bregmatic: from the center of anterior fontanelle (bregma) to the occipital protuberance, measuring 9.5 cm. This is the presenting diameter in vertex presentation. 
• Suboccipito-frontal: from the anterior part of bregma to the occipital protuberance, measuring 10 cm 
• Occipito-frontal: from the root of the nose to the most prominent part of the occiput, measuring 11.5cm
• Submento-bregmatic: from the center of the bregma to the angle of the mandible, measuring 9.5 cm. This is the presenting diameter in face presentation where the neck is hyperextended. 
• Submento-vertical: from the midpoint between fontanelles and the angle of the mandible, measuring 11.5cm 
• Occipito-mental: from the midpoint between fontanelles and the tip of the chin, measuring 13.5 cm. It is the presenting diameter in brow presentation. 

Cardinal Movements of Normal Labor

• Neck flexion
• Internal rotation
• Extension (delivers head)
• External rotation (Restitution)
• Expulsion (delivery of anterior and posterior shoulders)

Some of the key movements are not possible in the face or brow presentations.  

Based on the information provided above, it is obvious that labor will be arrested in brow presentation unless it spontaneously changes to face or vertex, as the occipito-mental diameter of the fetal head is significantly wider than the smallest diameter of the female pelvis. Face presentation can, however, be delivered vaginally, and further mechanisms of face delivery will be explained in later sections.

• Indications

As mentioned previously, spontaneous vaginal delivery can be successful in face presentation. However, the main indication for vaginal delivery in such circumstances would be a maternal choice. It is crucial to have a thorough conversation with a mother, explaining the risks and benefits of vaginal delivery with face presentation and a cesarean section. Informed consent and creating a rapport with the mother is an essential aspect of safe and successful labor.

• Contraindications

Vaginal delivery of face presentation is contraindicated if the mentum is lying posteriorly or is in a transverse position. In such a scenario, the fetal brow is pressing against the maternal symphysis pubis, and the short fetal neck, which is already maximally extended, cannot span the surface of the maternal sacrum. In this position, the diameter of the head is larger than the maternal pelvis, and it cannot descend through the birth canal. Therefore the cesarean section is recommended as the safest mode of delivery for mentum posterior face presentations. 

Attempts to manually convert face presentation to vertex, manual or forceps rotation of the persistent posterior chin to anterior are contraindicated as they can be dangerous.

Persistent brow presentation itself is a contraindication for vaginal delivery unless the fetus is significantly small or the maternal pelvis is large.

Continuous electronic fetal heart rate monitoring is recommended for face and brow presentations, as heart rate abnormalities are common in these scenarios. One study found that only 14% of the cases with face presentation had no abnormal traces on the cardiotocograph. [8] It is advised to use external transducer devices to prevent damage to the eyes. When internal monitoring is inevitable, it is suggested to place monitoring devices on bony parts carefully. 

People who are usually involved in the delivery of face/ brow presentation are:

• Experienced midwife, preferably looking after laboring woman 1:1
• Senior obstetrician 
• Neonatal team - in case of need for resuscitation 
• Anesthetic team - to provide necessary pain control (e.g., epidural)
• Theatre team  - in case of failure to progress and an emergency cesarean section will be required.
• Preparation

No specific preparation is required for face or brow presentation. However, it is essential to discuss the labor options with the mother and birthing partner and inform members of the neonatal, anesthetic, and theatre co-ordinating teams.

• Technique or Treatment

Mechanism of Labor in Face Presentation

During contractions, the pressure exerted by the fundus of the uterus on the fetus and pressure of amniotic fluid initiate descent. During this descent, the fetal neck extends instead of flexing. The internal rotation determines the outcome of delivery, if the fetal chin rotates posteriorly, vaginal delivery would not be possible, and cesarean section is permitted. The approach towards mentum-posterior delivery should be individualized, as the cases are rare. Expectant management is acceptable in multiparous women with small fetuses, as a spontaneous mentum-anterior rotation can occur. However, there should be a low threshold for cesarean section in primigravida women or women with large fetuses.

When the fetal chin is rotated towards maternal symphysis pubis as described as mentum-anterior; in these cases further descend through the vaginal canal continues with approximately 73% cases deliver spontaneously. [9] Fetal mentum presses on the maternal symphysis pubis, and the head is delivered by flexion. The occiput is pointing towards the maternal back, and external rotation happens. Shoulders are delivered in the same manner as in vertex delivery.

Mechanism of Labor in Brow Presentation

As this presentation is considered unstable, it is usually converted into a face or an occiput presentation. Due to the cephalic diameter being wider than the maternal pelvis, the fetal head cannot engage; thus, brow delivery cannot take place. Unless the fetus is small or the pelvis is very wide, the prognosis for vaginal delivery is poor. With persistent brow presentation, a cesarean section is required for safe delivery.

• Complications

As the cesarean section is becoming a more accessible mode of delivery in malpresentations, the incidence of maternal and fetal morbidity and mortality during face presentation has dropped significantly. [10]

However, there are still some complications associated with the nature of labor in face presentation. Due to the fetal head position, it is more challenging for the head to engage in the birth canal and descend, resulting in prolonged labor.

Prolonged labor itself can provoke foetal distress and arrhythmias. If the labor arrests or signs of fetal distress appear on CTG, the recommended next step in management is an emergency cesarean section, which in itself carries a myriad of operative and post-operative complications.

Finally, due to the nature of the fetal position and prolonged duration of labor in face presentation, neonates develop significant edema of the skull and face. Swelling of the fetal airway may also be present, resulting in respiratory distress after birth and possible intubation.

• Clinical Significance

During vertex presentation, the fetal head flexes, bringing the chin to the chest, forming the smallest possible fetal head diameter, measuring approximately 9.5cm. With face and brow presentation, the neck hyperextends, resulting in greater cephalic diameters. As a result, the fetal head will engage later, and labor will progress more slowly. Failure to progress in labor is also more common in both presentations compared to vertex presentation.

Furthermore, when the fetal chin is in a posterior position, this prevents further flexion of the fetal neck, as browns are pressing on the symphysis pubis. As a result, descend through the birth canal is impossible. Such presentation is considered undeliverable vaginally and requires an emergency cesarean section.

Manual attempts to change face presentation to vertex, manual or forceps rotation to mentum anterior are considered dangerous and are discouraged.

• Enhancing Healthcare Team Outcomes

A multidisciplinary team of healthcare experts supports the woman and her child during labor and the perinatal period. For a face or brow presentation to be appropriately diagnosed, an experienced midwife and obstetrician must be involved in the vaginal examination and labor monitoring. As fetal anomalies, such as anencephaly or goiter, can contribute to face presentation, sonographers experienced in antenatal scanning should also be involved in the care. It is advised to inform the anesthetic and neonatal teams in advance of the possible need for emergency cesarean section and resuscitation of the neonate. [11] [12]

• Review Questions
• Access free multiple choice questions on this topic.
• Comment on this article.

Disclosure: Julija Makajeva declares no relevant financial relationships with ineligible companies.

Disclosure: Mohsina Ashraf declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

• Cite this Page Makajeva J, Ashraf M. Delivery, Face and Brow Presentation. [Updated 2023 Jan 9]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

In this Page

Bulk download.

• Bulk download StatPearls data from FTP

Related information

• PubMed Links to PubMed

Similar articles in PubMed

• Sonographic diagnosis of fetal head deflexion and the risk of cesarean delivery. [Am J Obstet Gynecol MFM. 2020] Sonographic diagnosis of fetal head deflexion and the risk of cesarean delivery. Bellussi F, Livi A, Cataneo I, Salsi G, Lenzi J, Pilu G. Am J Obstet Gynecol MFM. 2020 Nov; 2(4):100217. Epub 2020 Aug 18.
• Review Sonographic evaluation of the fetal head position and attitude during labor. [Am J Obstet Gynecol. 2022] Review Sonographic evaluation of the fetal head position and attitude during labor. Ghi T, Dall'Asta A. Am J Obstet Gynecol. 2022 Jul 6; . Epub 2022 Jul 6.
• Stages of Labor. [StatPearls. 2024] Stages of Labor. Hutchison J, Mahdy H, Hutchison J. StatPearls. 2024 Jan
• Leopold Maneuvers. [StatPearls. 2024] Leopold Maneuvers. Superville SS, Siccardi MA. StatPearls. 2024 Jan
• Review Labor with abnormal presentation and position. [Obstet Gynecol Clin North Am. ...] Review Labor with abnormal presentation and position. Stitely ML, Gherman RB. Obstet Gynecol Clin North Am. 2005 Jun; 32(2):165-79.

Recent Activity

• Delivery, Face and Brow Presentation - StatPearls Delivery, Face and Brow Presentation - StatPearls

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

Connect with NLM

National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894

Web Policies FOIA HHS Vulnerability Disclosure

Help Accessibility Careers

An official website of the United States government

Here’s how you know

Official websites use .gov A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS A lock ( Lock Locked padlock icon ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

• Health Topics
• Drugs & Supplements
• Medical Tests
• Medical Encyclopedia
• About MedlinePlus
• Customer Support

Delivery presentations

Delivery presentation describes the way the baby is positioned to come down the birth canal for delivery.

Your baby must pass through your pelvic bones to reach the vaginal opening. The ease at which this passage will take place depends on how your baby is positioned during delivery. The best position for the baby to be in to pass through the pelvis is with the head down and the body facing towards the mother's back. This position is called occiput anterior (OA).

In breech position, the baby's bottom is facing down instead of the head. Your health care provider will most often detect this in an office visit before your labor begins. Most babies will be in the head-down position by about 34 weeks.

Part of your prenatal care after 34 weeks will involve making sure your baby is in the head-down position.

If your baby is breech, it is not safe to deliver vaginally. If your baby is not in a head-down position after your 36th week, your provider can explain your choices and their risks to help you decide what steps to take next.

Occiput Posterior (OP)

In occiput posterior position, your baby's head is down, but it is facing the mother's front instead of her back.

It is safe to deliver a baby facing this way. But it is harder for the baby to get through the pelvis. If a baby is in this position, sometimes it will rotate around during labor so that the head stays down and the body faces the mother's back (OA position).

The mother can walk, rock, and try different delivery positions during labor to help encourage the baby to turn. If the baby does not turn, labor can take longer. Sometimes, the provider may use forceps or a vacuum device to help get the baby out. If the baby stays in the OP position during labor, you have a higher risk of needing to deliver your baby by cesarean delivery (C-section).

Transverse Position

A baby in the transverse position is sideways. Often, the shoulders or back are over the mother's cervix. This is also called the shoulder, or oblique, position.

The risk for having a baby in the transverse position increases if you:

• Go into labor early
• Have given birth 3 or more times
• Have placenta previa

Unless your baby can be turned into head-down position, a vaginal birth will be too risky for you and your baby. A doctor will deliver your baby by cesarean birth ( C-section ).

Less Common Presentations

With the brow-first position, the baby's head extends backward (like looking up), and the forehead leads the way. This position may be more common if this is not your first pregnancy.

• Your provider rarely detects this position before labor. An ultrasound may be able to confirm a brow presentation.
• More likely, your provider will detect this position while you are in labor during an internal exam.

With face-first position, the baby's head is extended backwards even more than with brow first position.

• Most of the time, the force of contractions causes the baby to be in face-first position.
• It is also detected when labor does not progress.

In some of these presentations, a vaginal birth is possible, but labor will generally take longer. After delivery, the baby's face or brow will be swollen and may appear bruised. These changes will go away over the next few days.

Alternative Names

Pregnancy - delivery presentation; Labor - delivery presentation; Occiput posterior; Occiput anterior; Brow presentation

Barth WH. Malpresentations and malposition. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies . 8th ed. Philadelphia, PA: Elsevier; 2021:chap 17.

Thorp JM, Grantz KL. Clinical aspects of normal and abnormal labor. In: Lockwood CJ, Copel JA, Dugoff L, et al, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice . 9th ed. Philadelphia, PA: Elsevier; 2023:chap 40.

Vora S, Dobiesz VA. Emergency childbirth. In: Roberts JR, Custalow CB, Thomsen TW, eds. Roberts and Hedges' Clinical Procedures in Emergency Medicine and Acute Care . 7th ed. Philadelphia, PA: Elsevier; 2019:chap 56.

Review Date 11/21/2022

Updated by: LaQuita Martinez, MD, Department of Obstetrics and Gynecology, Emory Johns Creek Hospital, Alpharetta, GA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

Related MedlinePlus Health Topics

• Trying to Conceive
• Signs & Symptoms
• Pregnancy Tests
• Fertility Testing
• Fertility Treatment
• Weeks & Trimesters
• Staying Healthy
• Preparing for Baby
• Complications & Concerns
• Pregnancy Loss
• Breastfeeding
• School-Aged Kids
• Raising Kids
• Personal Stories
• Everyday Wellness
• Safety & First Aid
• Immunizations
• Food & Nutrition
• Active Play
• Pregnancy Products
• Nursery & Sleep Products
• Nursing & Feeding Products
• Clothing & Accessories
• Toys & Gifts
• Ovulation Calculator
• Pregnancy Due Date Calculator
• How to Talk About Postpartum Depression
• Editorial Process
• Meet Our Review Board

Fetal Positions for Labor and Birth

Knowing your baby's position can you help ease pain and speed up labor

In the last weeks of pregnancy , determining your baby's position can help you manage pain and discomfort. Knowing your baby's position during early labor can help you adjust your own position during labor and possibly even speed up the process.

Right or Left Occiput Anterior

Illustration by JR Bee, Verywell 

Looking at where the baby's head is in the birth canal helps determine the fetal position.The front of a baby's head is referred to as the anterior portion and the back is the posterior portion. There are two different positions called occiput anterior (OA) positions that may occur.

The left occiput anterior (LOA) position is the most common in labor. In this position, the baby's head is slightly off-center in the pelvis with the back of the head toward the mother's left thigh.

The right occiput anterior (ROA) presentation is also common in labor. In this position, the back of the baby is slightly off-center in the pelvis with the back of the head toward the mother's right thigh.

In general, OA positions do not lead to problems or additional pain during labor or birth.  

Right or Left Occiput Transverse

Illustration by JR Bee, Verywell  

When facing out toward the mother's right thigh, the baby is said to be left occiput transverse (LOT). This position is halfway between a posterior and anterior position. If the baby was previously in a posterior position (in either direction), the LOT position indicates positive movement toward an anterior position.

When the baby is facing outward toward the mother's left thigh, the baby is said to be right occiput transverse (ROT). Like the previous presentation, ROT is halfway between a posterior and anterior position. If the baby was previously in a posterior position, ROT is a sign the baby is making a positive move toward an anterior position.

When a baby is in the left occiput transverse position (LOT) or right occiput transverse (ROT) position during labor, it may lead to more pain and a slower progression.

Tips to Reduce Discomfort

There are several labor positions a mother can try to alleviate pain and encourage the baby to continue rotating toward an anterior position, including:

• Pelvic tilts
• Standing and swaying

A doula , labor nurse, midwife , or doctor may have other suggestions for positions.

Right or Left Occiput Posterior

When facing forward, the baby is in the occiput posterior position. If the baby is facing forward and slightly to the left (looking toward the mother's right thigh) it is in the left occiput posterior (LOP) position. This presentation can lead to more back pain (sometimes referred to as " back labor ") and slow progression of labor.

In the right occiput posterior position (ROP), the baby is facing forward and slightly to the right (looking toward the mother's left thigh). This presentation may slow labor and cause more pain.

To help prevent or decrease pain during labor and encourage the baby to move into a better position for delivery, mothers can try a variety of positions, including:

• Hands and knees
• Pelvic rocking

Mothers may try other comfort measures, including:

• Bathtub or shower (water)
• Counter pressure
• Movement (swaying, dancing, sitting on a birth ball )
• Rice socks (heat packs)

How a Doctor Determines Baby's Position

Leopold's maneuvers are a series of hands-on examinations your doctor or midwife will use to help determine your baby's position. During the third trimester , the assessment will be done at most of your prenatal visits.   Knowing the baby's position before labor begins can help you prepare for labor and delivery.

Once labor begins, a nurse, doctor, or midwife will be able to get a more accurate sense of your baby's position by performing a vaginal exam. When your cervix is dilated enough, the practitioner will insert their fingers into the vagina and feel for the suture lines of the baby's skull as it moves down in the birth canal.   It's important to ensure the baby is head down and moving in the right direction.

Labor and delivery may be more complicated if the baby is not in a head-down position, such as in the case of a breech presentation.

How You Can Determine Baby's Position

While exams by health practitioners are an important part of your care, from the prenatal period through labor and delivery, often the best person to assess a baby's position in the pelvis is you. Mothers should pay close attention to how the baby moves and where different movements are felt.

A technique called belly mapping can help mothers ask questions of themselves to assess their baby's movement and get a sense of the position they are in as labor approaches.

For example, the position of your baby's legs can be determined by asking questions about the location and strength of the kicking you feel. The spots where you feel the strongest kicks are most likely where your baby's feet are.

Other landmarks you can feel for include a large, flat plane, which is most likely your baby's back. Sometimes you can feel the baby arching his or her back.

At the top or bottom of the flat plane, you may feel either a hard, round shape (most likely your baby's head) or a soft curve (most likely to be your baby's bottom).

Guittier M, Othenin-Girard V, de Gasquet B, Irion O, Boulvain M. Maternal positioning to correct occiput posterior fetal position during the first stage of labour: a randomised controlled trial .  BJOG: An International Journal of Obstetrics & Gynaecology . 2016;123(13):2199-2207. doi:10.1111/1471-0528.13855

Gizzo S, Di Gangi S, Noventa M, Bacile V, Zambon A, Nardelli G. Women’s Choice of Positions during Labour: Return to the Past or a Modern Way to Give Birth? A Cohort Study in Italy .  Biomed Res Int . 2014;2014:1-7. doi:10.1155/2014/638093

Ahmad A, Webb S, Early B, Sitch A, Khan K, MacArthur C. Association between fetal position at onset of labor and mode of delivery: a prospective cohort study .  Ultrasound in Obstetrics & Gynecology . 2014;43(2):176-182. doi:10.1002/uog.13189

Nishikawa M, Sakakibara H. Effect of nursing intervention program using abdominal palpation of Leopold’s maneuvers on maternal-fetal attachment .  Reprod Health . 2013;10(1). doi:10.1186/1742-4755-10-12

Choi S, Park Y, Lee D, Ko H, Park I, Shin J. Sonographic assessment of fetal occiput position during labor for the prediction of labor dystocia and perinatal outcomes .  The Journal of Maternal-Fetal & Neonatal Medicine . 2016;29(24):3988-3992. doi:10.3109/14767058.2016.1152250

Bamberg C, Deprest J, Sindhwani N et al. Evaluating fetal head dimension changes during labor using open magnetic resonance imaging .  J Perinat Med . 2017;45(3). doi:10.1515/jpm-2016-0005

Gabbe S, Niebyl J, Simpson J et al.  Obstetrics . Philadelphia, Pa.: Elsevier; 2012.

By Robin Elise Weiss, PhD, MPH Robin Elise Weiss, PhD, MPH is a professor, author, childbirth and postpartum educator, certified doula, and lactation counselor.

• Getting Pregnant
• Registry Builder
• Baby Products
• Birth Clubs
• See all in Community
• Ovulation Calculator
• How To Get Pregnant
• How To Get Pregnant Fast
• Ovulation Discharge
• Implantation Bleeding
• Ovulation Symptoms
• Pregnancy Symptoms
• Am I Pregnant?
• Pregnancy Tests
• See all in Getting Pregnant
• Due Date Calculator
• Pregnancy Week by Week
• Pregnant Sex
• Weight Gain Tracker
• Signs of Labor
• Morning Sickness
• COVID Vaccine and Pregnancy
• Fetal Weight Chart
• Fetal Development
• Pregnancy Discharge
• Find Out Baby Gender
• Chinese Gender Predictor
• See all in Pregnancy
• Baby Name Generator
• Top Baby Names 2023
• Top Baby Names 2024
• How to Pick a Baby Name
• Most Popular Baby Names
• Baby Names by Letter
• Gender Neutral Names
• Unique Boy Names
• Unique Girl Names
• Top baby names by year
• See all in Baby Names
• Baby Development
• Baby Feeding Guide
• Newborn Sleep
• When Babies Roll Over
• First-Year Baby Costs Calculator
• Postpartum Health
• Baby Poop Chart
• See all in Baby
• Average Weight & Height
• Autism Signs
• Child Growth Chart
• Night Terrors
• Moving from Crib to Bed
• Toddler Feeding Guide
• Potty Training
• Bathing and Grooming
• See all in Toddler
• Height Predictor
• Potty Training: Boys
• Potty training: Girls
• How Much Sleep? (Ages 3+)
• Ready for Preschool?
• Thumb-Sucking
• Gross Motor Skills
• Napping (Ages 2 to 3)
• See all in Child
• Photos: Rashes & Skin Conditions
• Symptom Checker
• Vaccine Scheduler
• Reducing a Fever
• Acetaminophen Dosage Chart
• Constipation in Babies
• Ear Infection Symptoms
• Head Lice 101
• See all in Health
• Second Pregnancy
• Daycare Costs
• Family Finance
• Stay-At-Home Parents
• Breastfeeding Positions
• See all in Family
• Baby Sleep Training
• Preparing For Baby
• My Custom Checklist
• My Registries
• Take the Quiz
• Best Baby Products
• Best Breast Pump
• Best Convertible Car Seat
• Best Infant Car Seat
• Best Baby Bottle
• Best Baby Monitor
• Best Stroller
• Best Diapers
• Best Baby Carrier
• Best Diaper Bag
• Best Highchair
• See all in Baby Products
• Why Pregnant Belly Feels Tight
• Early Signs of Twins
• Teas During Pregnancy
• Baby Head Circumference Chart
• How Many Months Pregnant Am I
• What is a Rainbow Baby
• Braxton Hicks Contractions
• HCG Levels By Week
• When to Take a Pregnancy Test
• Am I Pregnant
• Why is Poop Green
• Can Pregnant Women Eat Shrimp
• Insemination
• UTI During Pregnancy
• Vitamin D Drops
• Best Baby Forumla
• Postpartum Depression
• Low Progesterone During Pregnancy
• Baby Shower
• Baby Shower Games

Breech, posterior, transverse lie: What position is my baby in?

Fetal presentation, or how your baby is situated in your womb at birth, is determined by the body part that's positioned to come out first, and it can affect the way you deliver. At the time of delivery, 97 percent of babies are head-down (cephalic presentation). But there are several other possibilities, including feet or bottom first (breech) as well as sideways (transverse lie) and diagonal (oblique lie).

Fetal presentation and position

During the last trimester of your pregnancy, your provider will check your baby's presentation by feeling your belly to locate the head, bottom, and back. If it's unclear, your provider may do an ultrasound or an internal exam to feel what part of the baby is in your pelvis.

Fetal position refers to whether the baby is facing your spine (anterior position) or facing your belly (posterior position). Fetal position can change often: Your baby may be face up at the beginning of labor and face down at delivery.

Here are the many possibilities for fetal presentation and position in the womb.

Medical illustrations by Jonathan Dimes

Head down, facing down (anterior position)

A baby who is head down and facing your spine is in the anterior position. This is the most common fetal presentation and the easiest position for a vaginal delivery.

This position is also known as "occiput anterior" because the back of your baby's skull (occipital bone) is in the front (anterior) of your pelvis.

Head down, facing up (posterior position)

In the posterior position , your baby is head down and facing your belly. You may also hear it called "sunny-side up" because babies who stay in this position are born facing up. But many babies who are facing up during labor rotate to the easier face down (anterior) position before birth.

Posterior position is formally known as "occiput posterior" because the back of your baby's skull (occipital bone) is in the back (posterior) of your pelvis.

Frank breech

In the frank breech presentation, both the baby's legs are extended so that the feet are up near the face. This is the most common type of breech presentation. Breech babies are difficult to deliver vaginally, so most arrive by c-section .

Some providers will attempt to turn your baby manually to the head down position by applying pressure to your belly. This is called an external cephalic version , and it has a 58 percent success rate for turning breech babies. For more information, see our article on breech birth .

Complete breech

A complete breech is when your baby is bottom down with hips and knees bent in a tuck or cross-legged position. If your baby is in a complete breech, you may feel kicking in your lower abdomen.

Incomplete breech

In an incomplete breech, one of the baby's knees is bent so that the foot is tucked next to the bottom with the other leg extended, positioning that foot closer to the face.

Single footling breech

In the single footling breech presentation, one of the baby's feet is pointed toward your cervix.

Double footling breech

In the double footling breech presentation, both of the baby's feet are pointed toward your cervix.

Transverse lie

In a transverse lie, the baby is lying horizontally in your uterus and may be facing up toward your head or down toward your feet. Babies settle this way less than 1 percent of the time, but it happens more commonly if you're carrying multiples or deliver before your due date.

If your baby stays in a transverse lie until the end of your pregnancy, it can be dangerous for delivery. Your provider will likely schedule a c-section or attempt an external cephalic version , which is highly successful for turning babies in this position.

Oblique lie

In rare cases, your baby may lie diagonally in your uterus, with his rump facing the side of your body at an angle.

Like the transverse lie, this position is more common earlier in pregnancy, and it's likely your provider will intervene if your baby is still in the oblique lie at the end of your third trimester.

Was this article helpful?

What to know if your baby is breech

What's a sunny-side up baby?

What happens to your baby right after birth

How your twins’ fetal positions affect labor and delivery

BabyCenter's editorial team is committed to providing the most helpful and trustworthy pregnancy and parenting information in the world. When creating and updating content, we rely on credible sources: respected health organizations, professional groups of doctors and other experts, and published studies in peer-reviewed journals. We believe you should always know the source of the information you're seeing. Learn more about our editorial and medical review policies .

Ahmad A et al. 2014. Association of fetal position at onset of labor and mode of delivery: A prospective cohort study. Ultrasound in obstetrics & gynecology 43(2):176-182. https://www.ncbi.nlm.nih.gov/pubmed/23929533 Opens a new window [Accessed September 2021]

Gray CJ and Shanahan MM. 2019. Breech presentation. StatPearls.  https://www.ncbi.nlm.nih.gov/books/NBK448063/ Opens a new window [Accessed September 2021]

Hankins GD. 1990. Transverse lie. American Journal of Perinatology 7(1):66-70.  https://www.ncbi.nlm.nih.gov/pubmed/2131781 Opens a new window [Accessed September 2021]

Medline Plus. 2020. Your baby in the birth canal. U.S. National Library of Medicine. https://medlineplus.gov/ency/article/002060.htm Opens a new window [Accessed September 2021]

Where to go next

• Type 2 Diabetes
• Heart Disease
• Digestive Health
• Multiple Sclerosis
• Diet & Nutrition
• Supplements
• Health Insurance
• Public Health
• Patient Rights
• Caregivers & Loved Ones
• End of Life Concerns
• Health News
• Thyroid Test Analyzer
• Doctor Discussion Guides
• Hemoglobin A1c Test Analyzer
• Lipid Test Analyzer
• Complete Blood Count (CBC) Analyzer
• What to Buy
• Editorial Process
• Meet Our Medical Expert Board

What Is Cephalic Position?

The ideal fetal position for labor and delivery

• Why It's Best

Risks of Other Positions

• Determining Position
• Turning a Fetus

The cephalic position is when a fetus is head down when it is ready to enter the birth canal. This is one of a few variations of how a fetus can rest in the womb and is considered the ideal one for labor and delivery.

About 96% of babies are born in the cephalic position. Most settle into it between the 32nd and 36th weeks of pregnancy . Your healthcare provider will monitor the fetus's position during the last weeks of gestation to ensure this has happened by week 36.

If the fetus is not in the cephalic position at that point, the provider may try to turn it. If this doesn't work, some—but not all—practitioners will attempt to deliver vaginally, while others will recommend a Cesarean (C-section).

Getty Images

Why Is the Cephalic Position Best?

During labor, contractions dilate the cervix so the fetus has adequate room to come through the birth canal. The cephalic position is the easiest and safest way for the baby to pass through the birth canal.

If the fetus is in a noncephalic position, delivery becomes more challenging. Different fetal positions have a range of difficulties and varying risks.

A small percentage of babies present in noncephalic positions. This can pose risks both to the fetus and the mother, and make labor and delivery more challenging. It can also influence the way in which someone can deliver.

A fetus may actually find itself in any of these positions throughout pregnancy, as the move about the uterus. But as they grow, there will be less room to tumble around and they will settle into a final position.

It is at this point that noncephalic positions can pose significant risks.

Cephalic Posterior

A fetus may also present in an occiput or cephalic posterior position. This means they are positioned head down, but they are facing the abdomen instead of the back.

This position is also nicknamed "sunny-side up."

Presenting this way increases the chance of a painful and prolonged delivery.

There are three different types of breech fetal positioning:

• Frank breech: The legs are up with the feet near the head.
• Footling breech: One or both legs is lowered over the cervix.
• Complete breech: The fetus is bottom-first with knees bent.

A vaginal delivery is most times a safe way to deliver. But with breech positions, a vaginal delivery can be complicated.

When a baby is born in the breech position, the largest part—its head—is delivered last. This can result in them getting stuck in the birth canal (entrapped). This can cause injury or death.

The umbilical cord may also be damaged or slide down into the mouth of the womb, which can reduce or cut off the baby's oxygen supply.

Some providers are still comfortable performing a vaginal birth as long as the fetus is doing well. But breech is always a riskier delivery position compared with the cephalic position, and most cases require a C-section.

Likelihood of a Breech Baby

You are more likely to have a breech baby if you:

• Go into early labor before you're full term
• Have an abnormally shaped uterus, fibroids , or too much amniotic fluid
• Are pregnant with multiples
• Have placenta previa (when the placenta covers the cervix)

Transverse Lie

In transverse lie position, the fetus is presenting sideways across the uterus rather than vertically. They may be:

• Down, with the back facing the birth canal
• With one shoulder pointing toward the birth canal
• Up, with the hands and feet facing the birth canal

If a transverse lie is not corrected before labor, a C-section will be required. This is typically the case.

Determining Fetal Position

Your healthcare provider can determine if your baby is in cephalic presentation by performing a physical exam and ultrasound.

In the final weeks of pregnancy, your healthcare provider will feel your lower abdomen with their hands to assess the positioning of the baby. This includes where the head, back, and buttocks lie

If your healthcare provider senses that the fetus is in a breech position, they can use ultrasound to confirm their suspicion.

Turning a Fetus So They Are in Cephalic Position

External cephalic version (ECV) is a common, noninvasive procedure to turn a breech baby into cephalic position while it's still in the uterus.

This is only considered if a healthcare provider monitors presentation progress in the last trimester and notices that a fetus is maintaining a noncephalic position as your delivery date approaches.

External Cephalic Version (ECV)

ECV involves the healthcare provider applying pressure to your stomach to turn the fetus from the outside. They will attempt to rotate the head forward or backward and lift the buttocks in an upward position. Sometimes, they use ultrasound to help guide the process.

The best time to perform ECV is about 37 weeks of pregnancy. Afterward, the fetal heart rate will be monitored to make sure it’s within normal levels. You should be able to go home after having ECV done.

ECV has a 50% to 60% success rate. However, even if it does work, there is still a chance the fetus will return to the breech position before birth.

Natural Methods For Turning a Fetus

There are also natural methods that can help turn a fetus into cephalic position. There is no medical research that confirms their efficacy, however.

• Changing your position: Sometimes a fetus will move when you get into certain positions. Two specific movements that your provider may recommend include: Getting on your hands and knees and gently rocking back and forth. Another you could try is pushing your hips up in the air while laying on your back with your knees bent and feet flat on the floor (bridge pose).
• Playing stimulating sounds: Fetuses gravitate to sound. You may be successful at luring a fetus out of breech position by playing music or a recording of your voice near your lower abdomen.
• Chiropractic care: A chiropractor can try the Webster technique. This is a specific chiropractic analysis and adjustment which enables chiropractors to establish balance in the pregnant person's pelvis and reduce undue stress to the uterus and supporting ligaments.
• Acupuncture: This is a considerably safe way someone can try to turn a fetus. Some practitioners incorporate moxibustion—the burning of dried mugwort on certain areas of the body—because they believe it will enhance the chances of success.

A Word From Verywell

While most babies are born in cephalic position at delivery, this is not always the case. And while some fetuses can be turned, others may be more stubborn.

This may affect your labor and delivery wishes. Try to remember that having a healthy baby, and staying well yourself, are your ultimate priorities. That may mean diverting from your best laid plans.

Speaking to your healthcare provider about turning options and the safest route of delivery may help you adjust to this twist and feel better about how you will move ahead.

Glezerman M. Planned vaginal breech delivery: current status and the need to reconsider . Expert Rev Obstet Gynecol. 2012;7(2):159-166. doi:10.1586/eog.12.2

Cleveland Clinic. Fetal positions for birth .

MedlinePlus. Breech birth .

UT Southwestern Medical Center. Can you turn a breech baby around?

The American College of Obstetricians and Gynecologists. If your baby is breech .

Roecker CB. Breech repositioning unresponsive to Webster technique: coexistence of oligohydramnios .  Journal of Chiropractic Medicine . 2013;12(2):74-78. doi:10.1016/j.jcm.2013.06.003

By Cherie Berkley, MS Berkley is a journalist with a certification in global health from Johns Hopkins University and a master's degree in journalism.

Fastest Obstetric, Gynecology and Pediatric Insight Engine

• Abdominal Key
• Anesthesia Key
• Basicmedical Key
• Otolaryngology & Ophthalmology
• Musculoskeletal Key
• Obstetric, Gynecology and Pediatric
• Oncology & Hematology
• Plastic Surgery & Dermatology
• Clinical Dentistry
• Radiology Key
• Thoracic Key
• Veterinary Medicine
• Gold Membership

Normal Labor and Delivery

Key Abbreviations American Academy of Pediatrics AAP American College of Obstetricians and Gynecologists ACOG Body mass index BMI California Maternal Quality Care Collaborative CMQCC Cephalopelvic disproportion CPD Cervical length CL Computed tomography CT Dehydroepiandrosterone sulfate DHEAS Fetal heart rate FHR Intrauterine pressure catheter IUPC Intraventricular hemorrhage IVH Left occiput anterior LOA Magnetic resonance imaging MRI Montevideo unit MVU Normal saline NS Occiput anterior OA Occiput posterior OP Occiput transverse OT Prostaglandin PG Randomized controlled trial RCT Right occiput anterior ROA Skin-to-skin contact SSC Society for Maternal-Fetal Medicine SMFM Overview The initiation of normal labor at term requires endocrine, paracrine, and autocrine signaling between the fetus, uterus, placenta, and the mother. Although the exact trigger for human labor at term remains unknown, it is believed to involve conversion of fetal dehydroepiandrosterone sulfate (DHEAS) to estriol and estradiol by the placenta. These hormones upregulate transcription of progesterone, progesterone receptors, oxytocin receptors, and gap junction proteins within the uterus, which helps to facilitate regular uterine contractions. The latent phase of labor is characterized by a slower rate of cervical dilation, whereas the active phase of labor is characterized by a faster rate of cervical dilation and does not begin for most women until the cervix is dilated 6 cm. The duration of the second stage of labor can be affected by a number of factors including epidural use, fetal position, fetal weight, ethnicity, and parity. This chapter will review the characteristics and physiology of normal labor at term. Factors that affect the average duration of the first and second stage of labor progress will be reviewed, and an evidence-based evaluation of strategies to support the mother during labor and facilitate safe delivery of the fetus will be presented. Labor: Definition and Physiology Labor is defined as the process by which the fetus is expelled from the uterus. More specifically, labor requires regular, effective contractions that lead to dilation and effacement of the cervix. This chapter describes the physiology and normal characteristics of term labor and delivery. The physiology of labor initiation has not been completely elucidated, but the putative mechanisms have been well reviewed by Liao and colleagues. Labor initiation is species specific, and the mechanisms of human labor are unique. The four phases of labor from quiescence to involution are outlined in Figure 12-1 . The first phase is quiescence, which represents that time in utero before labor begins, when uterine activity is suppressed by the action of progesterone, prostacyclin, relaxin, nitric oxide, parathyroid hormone–related peptide, and possibly other hormones. During the activation phase , estrogen begins to facilitate expression of myometrial receptors for prostaglandins (PGs) and oxytocin, which results in ion channel activation and increased gap junctions. This increase in the gap junctions between myometrial cells facilitates effective contractions. In essence, the activation phase readies the uterus for the subsequent stimulation phase , when uterotonics—particularly PGs and oxytocin—stimulate regular contractions. In the human, this process at term may be protracted, occurring over days to weeks. The final phase, uterine involution , occurs after delivery and is mediated primarily by oxytocin. The first three phases of labor require endocrine, paracrine, and autocrine interaction between the fetus, membranes, placenta, and mother. FIG 12-1 Regulation of uterine activity during pregnancy and labor. (Modified from Challis JRG, Gibb W. Control of parturition. Prenat Neonat Med. 1996;1:283.) The fetus has a central role in the initiation of term labor in nonhuman mammals; in humans, the fetal role is not completely understood ( Fig. 12-2 ). In sheep, term labor is initiated through activation of the fetal hypothalamic-pituitary-adrenal (HPA) axis, with a resultant increase in fetal adrenocorticotropic hormone (ACTH) and cortisol. Fetal cortisol increases production of estradiol and decreases production of progesterone by a shift in placental metabolism of cortisol dependent on placental 17α-hydroxylase. The change in the circulating progesterone/estradiol concentration stimulates placental production of oxytocin and PG, particularly PGF 2α , which in turn promotes myometrial contractility. If this increase in fetal ACTH and cortisol is blocked, progesterone levels remain unchanged, and parturition is delayed. In contrast, humans lack placental 17α-hydroxylase, maternal and fetal levels of progesterone remain elevated, and no trigger exists for parturition because of an increase in fetal cortisol near term. Rather, in humans, evidence suggests that placental production of corticotropin-releasing hormone (CRH) near term activates the fetal hypothalamic-pituitary axis and results in increased production of dehydroepiandrostenedione by the fetal adrenal gland. Fetal dehydroepiandrostenedione is converted in the placenta to estradiol and estriol. Placenta-derived estriol potentiates uterine activity by enhanc­ing the transcription of maternal (likely decidual) PGF 2α , PG receptors, oxytocin receptors, and gap-junction proteins. In humans, no documented decrease in progesterone has been observed near term, and a fall in progesterone is not necessary for labor initiation. However, some research suggests the possibility of a functional progesterone withdrawal in humans. Labor is accompanied by a decrease in the concentration of progesterone receptors and a change in the ratio of progesterone receptor isoforms A and B in both the myometrium and the membranes. During labor, increased expression of nuclear and membrane progesterone receptor isoforms serve to enhance genomic expression of contraction-associated proteins, increase intracellular calcium, and decrease cyclic adenosine monophosphate (cAMP). More research is needed to elucidate the precise mechanism through which the human parturition cascade is activated. Fetal maturation might play an important role as might maternal cues that affect circadian cycling. Most species have distinct diurnal patterns of contractions and delivery, and in humans, the majority of contractions occur at night. FIG 12-2 Proposed “parturition cascade” for labor induction at term. The spontaneous induction of labor at term in the human is regulated by a series of paracrine/autocrine hormones acting in an integrated parturition cascade responsible for promoting uterine contractions. PGE 2 , prostaglandin E 2 ; PGEM, 13,14-dihydro-15-keto-PGE 2 ; PGF 2α , prostaglandin F 2α ; PGFM, 13, 14-dihydro-15keto-PGF 2α . (Modified from Norwitz ER, Robinson JN, Repke JT. The initiation of parturition: a comparative analysis across the species. Curr Prob Obstet Gynecol Fertil. 1999;22:41.) Oxytocin is commonly used for labor induction and augmentation, and a full understanding of the mechanism of oxytocin action is important. Oxytocin is a peptide hormone synthesized in the hypothalamus and released from the posterior pituitary in a pulsatile fashion. At term, oxytocin serves as a potent uterotonic agent capable of stimulating uterine contractions at intravenous (IV) infusion rates of 1 to 2 mIU/min. Oxytocin is inactivated largely in the liver and kidney, and during pregnancy, it is degraded primarily by placental oxytocinase. Its biologic half-life is approximately 3 to 4 minutes, but it appears to be shorter when higher doses are infused. Concentrations of oxytocin in the maternal circulation do not change significantly during pregnancy or before the onset of labor, but they do rise late in the second stage of labor. Studies of fetal pituitary oxytocin production and the umbilical arteriovenous differences in plasma oxytocin strongly suggest that the fetus secretes oxytocin that reaches the maternal side of the placenta. The calculated rate of active oxytocin secretion from the fetus increases from a baseline of 1 mIU/min before labor to around 3 mIU/min after spontaneous labor. Significant differences in myometrial oxytocin receptor distribution have been reported, with large numbers of fundal receptors and fewer receptors in the lower uterine segment and cervix. Myometrial oxytocin receptors increase on average by 100- to 200-fold during pregnancy and reach a maximum during early labor. This rise in receptor concentration is paralleled by an increase in uterine sensitivity to circulating oxytocin. Specific high-affinity oxytocin receptors have also been isolated from human amnion and decidua parietalis but not decidua vera. It has been suggested that oxytocin plays a dual role in parturition. First, through its receptor, oxytocin directly stimulates uterine contractions. Second, oxytocin may act indirectly by stimulating the amnion and decidua to produce PG. Indeed, even when uterine contractions are adequate, induction of labor at term is successful only when oxytocin infusion is associated with an increase in PGF production. Oxytocin binding to its receptor activates phospholipase C. In turn, phospholipase C increases intracellular calcium both by stimulating the release of intracellular calcium and by promoting the influx of extracellular calcium. Oxytocin stimulation of phospholipase C can be inhibited by increased levels of cAMP. Increased calcium levels stimulate the calmodulin-mediated activation of myosin light-chain kinase. Oxytocin may also stimulate uterine contractions via a calcium-independent pathway by inhibiting myosin phosphatase, which in turn increases myosin phosphorylation. These pathways (of PGF 2α and intracellular calcium) have been the target of multiple tocolytic agents: indomethacin, calcium channel blockers, β-mimetics (through stimulation of cAMP), and magnesium. Mechanics of Labor Labor and delivery are not passive processes in which uterine contractions push a rigid object through a fixed aperture. The ability of the fetus to successfully negotiate the pelvis during labor and delivery depends on the complex interactions of three variables: uterine activity, the fetus, and the maternal pelvis. This complex relationship has been simplified in the mnemonic powers, passenger, passage . Uterine Activity (Powers) The powers refer to the forces generated by the uterine musculature. Uterine activity is characterized by the frequency, amplitude (intensity), and duration of contractions. Assessment of uterine activity may include simple observation, manual palpation, external objective assessment techniques (such as external tocodynamometry), and direct measurement via an intrauterine pressure catheter (IUPC). External tocodynamometry measures the change in shape of the abdominal wall as a function of uterine contractions and, as such, is qualitative rather than quantitative. Although it permits graphic display of uterine activity and allows for accurate correlation of fetal heart rate (FHR) patterns with uterine activity, external tocodynamometry does not allow measurement of contraction intensity or basal intrauterine tone. The most precise method for determination of uterine activity is the direct measurement of intrauterine pressure with an IUPC . However, this procedure should not be performed unless indicated given the small but finite associated risks of uterine perforation, placental disruption, and intrauterine infection. Despite technologic improvements, the definition of “adequate” uterine activity during labor remains unclear. Classically, three to five contractions in 10 minutes has been used to define adequate labor; this pattern has been observed in approximately 95% of women in spontaneous labor. In labor, patients usually contract every 2 to 5 minutes, with contractions becoming as frequent as every 2 to 3 minutes in late active labor and during the second stage. Abnormal uterine activity can also be observed either spontaneously or as a result of iatrogenic interventions. Tachysystole is defined as more than five contractions in 10 minutes averaged over 30 minutes. If tachysytole occurs, documentation should note the presence or absence of FHR decelerations. The term hyperstimulation should no longer be used. Various units of measure have been devised to objectively quantify uterine activity, the most common of which is the Montevideo unit (MVU) , a measure of average frequency and amplitude above basal tone (the average strength of contractions in millimeters of mercury multiplied by the number of contractions per 10 min). Although 150 to 350 MVU has been described for adequate labor, 200 to 250 MVU is commonly accepted to define adequate labor in the active phase. No data identify adequate forces during latent labor. Although it is generally believed that optimal uterine contractions are associated with an increased likelihood of vaginal delivery, data are limited to support this assumption. If uterine contractions are “adequate” to effect vaginal delivery, one of two things will happen: either the cervix will efface and dilate, and the fetal head will descend, or caput succedaneum (scalp edema) and molding of the fetal head (overlapping of the skull bones) will worsen without cervical effacement and dilation. The latter situation suggests the presence of cephalopelvic disproportion (CPD), which can be either absolute , in which the fetus is simply too large to negotiate the pelvis, or relative , in which delivery of the fetus through the pelvis would be possible under optimal conditions but is precluded by malposition or abnormal attitude of the fetal head. Fetus (Passenger) The passenger, of course, is the fetus. Several fetal variables influence the course of labor and delivery. Fetal size can be estimated clinically by abdominal palpation or ultrasound or by asking a multiparous patient about her best estimate, but all of these methods are subject to a large degree of error. Fetal macrosomia is defined by the American College of Obstetricians and Gynecologists (ACOG) as birthweight greater than or equal to the 90th percentile for a given gestational age or greater than 4500 g for any gestational age, and it is associated with an increased likelihood of planned cesarean delivery, labor dystocia, cesarean delivery after a failed trial of labor, shoulder dystocia, and birth trauma. Fetal lie refers to the longitudinal axis of the fetus relative to the longitudinal axis of the uterus. Fetal lie can be longitudinal, transverse, or oblique ( Fig. 12-3 ). In a singleton pregnancy, only fetuses in a longitudinal lie can be safely delivered vaginally. FIG 12-3 Examples of fetal lie. Presentation refers to the fetal part that directly overlies the pelvic inlet. In a fetus presenting in the longitudinal lie, the presentation can be cephalic (vertex) or breech. Compound presentation refers to the presence of more than one fetal part overlying the pelvic inlet, such as a fetal hand and the vertex. Funic presentation refers to presentation of the umbilical cord and is rare at term. In a cephalic fetus, the presentation is classified according to the leading bony landmark of the skull, which can be either the occiput (vertex), the chin (mentum), or the brow ( Fig. 12-4 ). Malpresentation , a term that refers to any presentation other than vertex, is seen in approximately 5% of all term labors (see Chapter 17 ). FIG 12-4 Landmarks of fetal skull for determination of fetal position. Attitude refers to the position of the head with regard to the fetal spine (the degree of flexion and/or extension of the fetal head). Flexion of the head is important to facilitate engagement of the head in the maternal pelvis. When the fetal chin is optimally flexed onto the chest, the suboccipitobregmatic diameter (9.5 cm) presents at the pelvic inlet ( Fig. 12-5 ). This is the smallest possible presenting diameter in the cephalic presentation. As the head deflexes (extends), the diameter presenting to the pelvic inlet progressively increases even before the malpresentations of brow and face are encountered (see Fig. 12-5 ) and may contribute to failure to progress in labor. The architecture of the pelvic floor along with increased uterine activity may correct deflexion in the early stages of labor. FIG 12-5 Presenting diameters of the average term fetal skull. Position of the fetus refers to the relationship of the fetal presenting part to the maternal pelvis, and it can be assessed most accurately on vaginal examination. For cephalic presentations, the fetal occiput is the reference: if the occiput is directly anterior, the position is occiput anterior (OA); if the occiput is turned toward the mother’s right side, the position is right occiput anterior (ROA). In the breech presentation, the sacrum is the reference (right sacrum anterior). The various positions of a cephalic presentation are illustrated in Figure 12-6 . In a vertex presentation, position can be determined by palpation of the fetal sutures: the sagittal suture is the easiest to palpate, but palpation of the distinctive lambdoid sutures should identify the position of the fetal occiput; the frontal suture can also be used to determine the position of the front of the vertex. FIG 12-6 Fetal presentations and positions in labor. LOA, left occiput anterior; LOP, left occiput posterior; LOT, left occiput transverse; ROA, right occiput anterior; ROT, right occiput transverse; ROP, right occiput posterior. (Modified from Norwitz ER, Robinson J, Repke JT. The initiation and management of labor. In Seifer DB, Samuels P, Kniss DA, eds. The Physiologic Basis of Gynecology and Obstetrics. Philadelphia: Lippincott, Williams & Wilkins; 2001.) Most commonly, the fetal head enters the pelvis in a transverse position and then, as a normal part of labor, it rotates to an OA position. Most fetuses deliver in the OA, left occiput anterior (LOA), or ROA position. Malposition refers to any position in labor that is not in the above three categories. In the past, fewer than 10% of presentations were occiput posterior (OP) at delivery. However, epidural analgesia may be an independent risk factor for persistent OP presentation in labor. In an observational cohort study, OP presentation was observed in 12.9% of women with epidurals compared with 3.3% of controls ( P = .002). In a Cochrane meta-analysis of four randomized controlled trials (RCTs), malposition was 40% more likely for women with an epidural compared with controls; however, this difference was not statistically significant, and more RCTs are needed (odds ratio [OR] 1.40; 95% confidence interval [CI], 0.98 to 1.99). Asynclitism occurs when the sagittal suture is not directly central relative to the maternal pelvis. If the fetal head is turned such that more parietal bone is present posteriorly, the sagittal suture is more anterior; this is referred to as posterior asynclitism. In contrast, anterior asynclitism occurs more parietal bone presents anteriorly. The occiput transverse (OT) and OP positions are less common at delivery and are more difficult to deliver. Station is a measure of descent of the bony presenting part of the fetus through the birth canal ( Fig. 12-7 ). The current standard classification (−5 to +5) is based on a quantitative measure in centimeters of the distance of the leading bony edge from the ischial spines. The midpoint (0 station) is defined as the plane of the maternal ischial spines. The ischial spines can be palpated on vaginal examination at approximately 8 o’clock and 4 o’clock. For the right-handed person, they are most easily felt on the maternal right. FIG 12-7 The relationship of the leading edge of the presenting part of the fetus to the plane of the maternal ischial spines determines the station. Station +1/+3 (old classification), or +2/+5 (new classification), is illustrated. An abnormality in any of these fetal variables may affect both the course of labor and the route of delivery. For example, OP presentation is well known to be associated with longer labor, operative vaginal delivery, and an increased risk of cesarean delivery. Maternal Pelvis (Passage) The passage consists of the bony pelvis—composed of the sacrum, ilium, ischium, and pubis—and the resistance provided by the soft tissues. The bony pelvis is divided into the false (greater) and true (lesser) pelvis by the pelvic brim, which is demarcated by the sacral promontory, the anterior ala of the sacrum, the arcuate line of the ilium, the pectineal line of the pubis, and the pubic crest culminating in the symphysis ( Fig. 12-8 ). Measurements of the various parameters of the bony female pelvis have been made with great precision, directly in cadavers and using radiographic imaging in living women. Such measurements have divided the true pelvis into a series of planes that must be negotiated by the fetus during passage through the birth canal, which can be broadly termed the pelvic inlet, midpelvis, and pelvic outlet. Pelvimetry performed with radiographic computed tomography (CT) or magnetic resonance imaging (MRI) has been used to determine average and critical limit values for the various parameters of the bony pelvis ( Table 12-1 ). Critical limit values are measurements that may be associated with a significant probability of CPD depending upon fetal size and gestational age. However, subsequent studies were unable to demonstrate threshold pelvic or fetal cutoff values with sufficient sensitivity or specificity to predict CPD and the subsequent need for cesarean delivery prior to the onset of labor. In current obstetric practice, radiographic CT and MRI pelvimetry are rarely used given the lack of evidence of benefit and some data that show possible harm (increased incidence of cesarean delivery); instead, a clinical trial of the pelvis (labor) is used. The remaining indications for radiography, CT pelvimetry, or MRI are evaluation for vaginal breech delivery or evaluation of a woman who has suffered a significant pelvic fracture. FIG 12-8 Superior (A) and anterior (B) view of the female pelvis. (From Repke JT. Intrapartum Obstetrics. New York: Churchill Livingstone; 1996;68.) TABLE 12-1 AVERAGE AND CRITICAL LIMIT VALUES FOR PELVIC MEASUREMENTS BY X-RAY PELVIMETRY DIAMETER AVERAGE VALUE CRITICAL LIMIT * Pelvic Inlet Anteroposterior (cm) 12.5 10.0 Transverse (cm) 13.0 12.0 Sum (cm) 25.5 22.0 Area (cm 2 ) 145.0 123.0 Pelvic Midcavity Anteroposterior (cm) 11.5 10.0 Transverse (cm) 10.5 9.5 Sum (cm) 22.0 19.5 Area (cm 2 ) 125.0 106.0   Modified from O’Brien WF, Cefalo RC. Labor and delivery. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: Normal and Problem Pregnancies, ed 3. New York: Churchill Livingstone; 1996;377. * The critical limit values cited imply a high likelihood of cephalopelvic disproportion. Clinical pelvimetry is currently the only method of assessing the shape and dimensions of the bony pelvis in labor. A useful protocol for clinical pelvimetry is detailed in Figure 12-9 and involves assessment of the pelvic inlet, midpelvis, and pelvic outlet. Reported average and critical-limit pelvic diameters may be used as a historical reference during the clinical examination to determine pelvic shape and assess risk for CPD. The inlet of the true pelvis is largest in its transverse diameter and averages 13.5 cm. The diagonal conjugate, the distance from the sacral promontory to the inferior margin of the symphysis pubis as assessed on vaginal examination, is a clinical representation of the anteroposterior (AP) diameter of the pelvic inlet. The true conjugate, or obstetric conjugate, of the pelvic inlet is the distance from the sacral promontory to the superior aspect of the symphysis pubis. The obstetric conjugate has an average value of 11 cm and is the smallest diameter of the inlet. It is considered to be contracted if it measures less than 10 cm. The obstetric conjugate cannot be measured clinically but can be estimated by subtracting 1.5 to 2.0 cm from the diagonal conjugate, which has an average distance of 12.5 cm. FIG 12-9 A protocol for clinical pelvimetry. The limiting factor in the midpelvis is the transverse interspinous diameter (the measurement between the ischial spines), which is usually the smallest diameter of the pelvis but should be greater than 10 cm. The pelvic outlet is rarely of clinical significance, however. The average pubic angle is greater than 90 degrees and will typically accommodate two fingerbreadths. The AP diameter from the coccyx to the symphysis pubis is approximately 13 cm in most cases, and the transverse diameter between the ischial tuberosities is approximately 8 cm and will typically accommodate four knuckles (see Fig. 12-9 ). The shape of the female bony pelvis can be classified into four broad categories: gynecoid, anthropoid, android, and platypelloid ( Fig. 12-10 ). This classification is based on the radiographic studies of Caldwell and Moloy and separates those with more favorable characteristics (gynecoid, anthropoid) from those less favorable for vaginal delivery (android, platypelloid). In reality, however, many women fall into intermediate classes, and the distinctions become arbitrary. The gynecoid pelvis is the classic female shape. The anthropoid pelvis—with its exaggerated oval shape of the inlet, largest AP diameter, and limited anterior capacity—is more often associated with delivery in the OP position. The android pelvis is male in pattern and theoretically has an increased risk of CPD, and the broad and flat platypelloid pelvis theoretically predisposes to a transverse arrest. Although the assessment of fetal size, along with pelvic shape and capacity, is still of clinical utility, it is a very inexact science. An adequate trial of labor is the only definitive method to determine whether a fetus will be able to safely negotiate through the pelvis. FIG 12-10 Characteristics of the four types of female bony pelvis. (Modified from Callahan TL, Caughey AB, Heffner LJ, eds. Blueprints in Obstetrics and Gynecology. Malden, MA: Blackwell Science; 1998;45.) Pelvic soft tissues may provide resistance in both the first and second stages of labor. In the first stage, resistance is offered primarily by the cervix, whereas in the second stage, it is offered by the muscles of the pelvic floor. In the second stage of labor, the resistance of the pelvic musculature is believed to play an important role in the rotation and movement of the presenting part through the pelvis. Cardinal Movements in Labor The cardinal movements refer to changes in the position of the fetal head during its passage through the birth canal. Because of the asymmetry of the shape of both the fetal head and the maternal bony pelvis, such rotations are required for the fetus to successfully negotiate the birth canal. Although labor and birth comprise a continuous process, seven discrete cardinal movements are described: (1) engagement, (2) descent, (3) flexion, (4) internal rotation, (5) extension, (6) external rotation or restitution, and (7) expulsion ( Fig. 12-11 ). FIG 12-11 Cardinal movements of labor. Engagement Engagement refers to passage of the widest diameter of the presenting part to a level below the plane of the pelvic inlet ( Fig. 12-12 ). In the cephalic presentation with a well-flexed head, the largest transverse diameter of the fetal head is the biparietal diameter (9.5 cm). In the breech, the widest diameter is the bitrochanteric diameter. Clinically, engagement can be confirmed by palpation of the presenting part both abdominally and vaginally. With a cephalic presentation, engagement is achieved when the presenting part is at zero station on vaginal examination. Engagement is considered an important clinical prognostic sign because it demonstrates that, at least at the level of the pelvic inlet, the maternal bony pelvis is sufficiently large to allow descent of the fetal head. In nulliparas, engagement of the fetal head usually occurs by 36 weeks’ gestation; however, in multiparas engagement can occur later in gestation or even during the course of labor. FIG 12-12 Engagement of the fetal head. Descent Descent refers to the downward passage of the presenting part through the pelvis. Descent of the fetus is not continuous; the greatest rates of descent occur in the late active phase and during the second stage of labor. Flexion Flexion of the fetal head occurs passively as the head descends owing to the shape of the bony pelvis and the resistance offered by the soft tissues of the pelvic floor. Although flexion of the fetal head onto the chest is present to some degree in most fetuses before labor, complete flexion usually occurs only during the course of labor. The result of complete flexion is to present the smallest diameter of the fetal head (the suboccipitobregmatic diameter) for optimal passage through the pelvis. Internal Rotation Internal rotation refers to rotation of the presenting part from its original position as it enters the pelvic inlet (usually OT) to the AP position as it passes through the pelvis. As with flexion, internal rotation is a passive movement that results from the shape of the pelvis and the pelvic floor musculature. The pelvic floor musculature, including the coccygeus and ileococcygeus muscles, forms a V -shaped “hammock” that diverges anteriorly. As the head descends, the occiput of the fetus rotates toward the symphysis pubis—or, less commonly, toward the hollow of the sacrum—thereby allowing the widest portion of the fetus to negotiate the pelvis at its widest dimension. Owing to the angle of inclination between the maternal lumbar spine and pelvic inlet, the fetal head engages in an asynclitic fashion (i.e., with one parietal eminence lower than the other). With uterine contractions, the leading parietal eminence descends and is first to engage the pelvic floor. As the uterus relaxes, the pelvic floor musculature causes the fetal head to rotate until it is no longer asynclitic. Extension Extension occurs once the fetus has descended to the level of the introitus. This descent brings the base of the occiput into contact with the inferior margin at the symphysis pubis. At this point, the birth canal curves upward. The fetal head is delivered by extension and rotates around the symphysis pubis. The forces responsible for this motion are the downward force exerted on the fetus by the uterine contractions along with the upward forces exerted by the muscles of the pelvic floor. External Rotation External rotation, also known as restitution, refers to the return of the fetal head to the correct anatomic position in relation to the fetal torso. This can occur to either side depending on the orientation of the fetus; this is again a passive movement that results from a release of the forces exerted on the fetal head by the maternal bony pelvis and its musculature and mediated by the basal tone of the fetal musculature. Expulsion Expulsion refers to delivery of the rest of the fetus. After delivery of the head and external rotation, further descent brings the anterior shoulder to the level of the symphysis pubis. The anterior shoulder is delivered in much the same manner as the head, with rotation of the shoulder under the symphysis pubis . After the shoulder, the rest of the body is usually delivered without difficulty. Normal Progress of Labor Progress of labor is measured with multiple variables. With the onset of regular contractions, the fetus descends in the pelvis as the cervix both effaces and dilates. With each vaginal examination to judge labor progress, the clinician must assess not only cervical effacement and dilation but fetal station and position. This assessment depends on skilled digital palpation of the maternal cervix and the presenting part. As the cervix dilates in labor, it thins and shortens—or becomes more effaced —over time. Cervical effacement refers to the length of the remaining cervix and can be reported in length or as a percentage. If percentage is used, 0% effacement at term refers to at least a 2 cm long or a very thick cervix, and 100% effacement refers to no length remaining or a very thin cervix. Most clinicians use percentages to follow cervical effacement during labor. Generally, 80% or greater effacement is observed in women who are in active labor. Dilation, perhaps the easiest assessment to master, ranges from closed (no dilation) to complete (10 cm dilated). For most women, a cervical dilation that accommodates a single index finger is equal to 1 cm, and two index fingers’ dilation is equal to 3 cm. If no cervix can be palpated around the presenting part, the cervix is 10 cm or completely dilated. The assessment of station, discussed earlier, is important for documentation of progress, but it is also critical when determining if an operative vaginal delivery is feasible. Fetal head position should be regularly determined once the woman is in active labor; ideally, this should occur before significant caput has developed, which obscures the sutures. Like station, knowledge of the fetal position is critical before performing an operative vaginal delivery (see Chapter 14 ). Labor occurs in three stages: the first stage is from labor onset until full dilation of the cervix; the second stage is from full cervical dilation until delivery of the baby; and the third stage begins with delivery of the baby and ends with delivery of the placenta. The first stage of labor is divided into two phases: the first is the latent phase, and the second is the active phase . The latent phase begins with the onset of labor and is characterized by regular, painful uterine contractions and a slow rate of cervical change. When the rate of cervical dilation is accelerated, latent labor ends and active labor begins. Labor onset is a retrospective diagnosis that is difficult to identify objectively. It is defined by the initiation of regular painful contractions of sufficient duration and intensity to result in cervical dilation or effacement. Women are frequently at home during this time; therefore the identification of labor onset depends on patient memory and the timing of contractions in relation to the cervical examination. The active phase of labor is defined as the period in which the greatest rate of cervical dilation occurs. Identification of the point at which labor transitions from the latent to the active phase will depend upon the frequency of cervical examinations and retrospective examination of labor progress. Historically, based upon Friedman’s seminal data on cervical dilation and labor progress from the 1950s and 1960s, active labor required 80% or more effacement and 4 cm or greater dilation of the cervix. He analyzed labor progress in 500 nulliparous and multiparous women and reported normative data that have been used for more than half a century to define our expectations of normal and abnormal labor. Friedman revolutionized our understanding of labor because he was able to plot static observations of cervical dilation against time and successfully translate the dynamic process of labor into a sigmoid-shaped curve ( Fig. 12-13 ). Friedman’s data popularized the use of the labor graph, which first depicted only cervical dilation and was then later modified to include fetal descent. Four-centimeter cervical dilation marks the transition from the latent to the active phase because it corresponds to the flexion point on the averaged labor curve generated from a review of 500 individual labor curves in the original Friedman dataset. Rates of 1.5 and 1.2 cm dilation per hour in the active phase for multiparous and nulliparous women, respectively, represent the 5th percentile of normal. These data have led to the general concept that in active labor, a rate of dilation of at least 1 cm per hour should occur. FIG 12-13 A, Modern labor graph. Characteristics of the average cervical dilation curve for nulliparous labor. B, Zhang labor partogram. The 95th percentiles of cumulative duration of labor from admission among singleton term nulliparous women with spontaneous onset of labor. Accel., acceleration; Decel., deceleration; Max., maximum; Sec., seconds. ( A, Modified from Friedman EA. Labor: Clinical Evaluation and Management, ed 2. Norwalk, CT: Appleton-Century-Crofts; 1978. B , From Zhang J, Landy H, Branch D, et al; the Consortium on Safe Labor. Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol. 2010;1116:1281.) More recent analysis of contemporary labor from several studies challenges our understanding of the cervical dilation at which active labor occurs and suggests that the transition from the latent phase to the active phase of labor is a more gradual process. An analysis of labor curves for 1699 multiparous and nulliparous women who presented in spontaneous labor at term and underwent a vaginal delivery determined that only half of the women with a cervical dilation of 4 cm were in the active phase. By 5 cm of cervical dilation, 75% of the women were in the active phase, and by 6 cm cervical dilation, 89% of the women were in the active phase. Zhang and colleagues reviewed data from the National Collaborative Perinatal Project, a historic cohort of 26,838 term parturients in spontaneous labor from 1959 through 1966. This study used a repeated measures analysis to construct labor curves for parturients whose intrapartum management was similar to those studied by Friedman in the 1950s. The cesarean delivery rate was 5.6%, and only 20% of nulliparas and 12% of multiparas received oxytocin for labor augmentation. This study determined that labor progress in nulliparous women who ultimately had a vaginal delivery is in fact slower than previously reported until 6 cm of cervical dilation. Specifically, most nulliparous women were not in active labor until approximately 5 to 6 cm of cervical dilation, and the slope of labor progress did not increase until after 6 cm. These findings were confirmed in an analysis of contemporary data collected prospectively by the Consortium on Safe Labor, which enrolled and followed 62,415 singleton term parturients who presented in spontaneous labor at 19 institutions from 2002 through 2007. This dataset included a greater percentage of women with oxytocin augmentation (45% to 47%) and epidural analgesia (71% to 84%) compared with those studied by Friedman in the 1950s. Zhang and colleagues reported the median and 95th percentile of time to progress from one centimeter to the next and confirmed that labor may take more than 6 hours to progress from 4 to 5 cm and more than 3 hours to progress from 5 to 6 cm regardless of parity ( Table 12-2 ). Multiparas had a faster rate of cervical dilation compared with nulliparas only after 6 cm of cervical dilation had been reached. These data suggest that it would be more appropriate to utilize a threshold of 6 cm cervical dilation to define active phase labor onset and that the rate of cervical dilation for nulliparas at the 95th percentile of normal may be greater than the 1 cm per hour previously expected. These are important findings that suggest clinicians using the Friedman dataset to determine the threshold for active labor may be diagnosing active phase arrest prematurely, which could result in unnecessary cesarean deliveries (see Chapter 13 ). TABLE 12-2 MEDIAN DURATION OF TIME ELAPSED IN HOURS FOR EACH CENTIMETER OF CHANGE IN CERVICAL DILATION IN SPONTANEOUS LABOR STRATIFIED BY PARITY CERVICAL DILATION (cm) PARITY 0 * PARITY 1 PARITY ≥2 3-4 1.8 (8.1) – – 4-5 1.3 (6.4) 1.4 ( 7.3) 1.4 (7.0) 5-6 0.8 (3.2) 0.8 (3.4) 0.8 (3.4) 6-7 0.6 (2.2) 0.5 (1.9) 0.5 (1.8) 7-8 0.5 (1.6) 0.4 (1.3) 0.4 (1.2) 8-9 0.5 (1.2) 0.3 (1.0) 0.3 (0.9) 9-10 0.5 (1.8) 0.3 (0.9) 0.3 (0.8)

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related posts:

• Antepartum Fetal Evaluation
• Cesarean Delivery
• Prolonged and Postterm Pregnancy
• Mental Health and Behavioral Disorders in Pregnancy

Stay updated, free articles. Join our Telegram channel

Comments are closed for this page.

Full access? Get Clinical Tree

In this Article

The ABCs of Cephalic Presentation: A Comprehensive Guide for Moms-to-Be

Updated on 24 November 2023

As expectant mothers eagerly anticipate the arrival of their little ones, understanding the intricacies of pregnancy becomes crucial. One term that frequently arises in discussions about childbirth is "cephalic presentation." In this article, we will understand its meaning, types, benefits associated with it, the likelihood of normal delivery and address common concerns expectant mothers might have.

What is the meaning of cephalic presentation in pregnancy?

Cephalic presentation means the baby's head is positioned down towards the birth canal, which is the ideal fetal position for childbirth. This position is considered optimal for a smoother and safer delivery. In medical terms, a baby in cephalic presentation is said to be in a "vertex" position.

The majority of babies naturally assume a cephalic presentation before birth. Other presentations, such as breech presentation (where the baby's buttocks or feet are positioned to enter the birth canal first) or transverse presentation (where the baby is lying sideways), may complicate the delivery process and may require medical intervention.

Cephalic presentation types

There are different types of cephalic presentation, each influencing the birthing process. The primary types include:

1. Vertex Presentation

The most common type where the baby's head is down, facing the mother's spine.

2. Brow Presentation

The baby's head is slightly extended, and the forehead presents first.

3. Face Presentation

The baby is positioned headfirst, but the face is the presenting part instead of the crown of the head.

Understanding these variations is essential for expectant mothers and healthcare providers to navigate potential challenges during labor.

You may also like: How to Get Baby in Right Position for Birth?

What are the benefits of cephalic presentation?

In order to understand whether cephalic presentation is good or bad, let’s take a look at its key advantages:

1. Easier Engagement

This presentation facilitates the baby's engagement in the pelvis, aiding in a smoother descent during labor.

2. Reduced Risk of Complications

Babies in head-first position typically experience fewer complications during delivery compared to other presentations.

3. Faster Labor Progression

This position is associated with quicker labor progression, leading to a potentially shorter and less stressful birthing process.

4. Lower Cesarean Section Rates

The chances of a cesarean section are significantly reduced when the baby is in cephalic presentation in pregnancy.

5. Optimal Fetal Oxygenation

The head-first position allows for optimal oxygenation of the baby as the head can easily pass through the birth canal, promoting a healthy start to life.

What are the chances of normal delivery in cephalic presentation?

The chances of a normal delivery are significantly higher when the baby is in cephalic or head-first presentation. Vaginal births are the natural outcome when the baby's head leads the way, aligning with the natural mechanics of childbirth.

While this presentation increases the chances of a normal delivery, it's important to note that individual factors, such as the mother's pelvic shape, the size of the baby, and the progress of labor, can also influence the delivery process. Sometimes complications may arise during labor and medical interventions or a cesarean section may be necessary.

You may also like: Normal Delivery Tips: An Expecting Mother's Guide to a Smooth Childbirth Experience

How to achieve cephalic presentation in pregnancy?

While fetal positioning is largely influenced by genetic and environmental factors, there are strategies to encourage head-first fetal position:

1. Regular Exercise

Engaging in exercises such as pelvic tilts and knee-chest exercises may help promote optimal fetal positioning.

2. Correct Posture

Maintaining good posture, particularly during the third trimester , can influence fetal positioning.

3. Hands and Knees Position

Spend some time on your hands and knees. This position may help the baby settle into the pelvis with the head down.

4. Forward-leaning Inversion

Under the guidance of a qualified professional, some women try forward-leaning inversions to encourage the baby to move into a head-down position. This involves positioning the body with the hips higher than the head.

5. Prenatal Yoga

Prenatal yoga focuses on strengthening the pelvic floor and promoting flexibility, potentially aiding in cephalic presentation.

6. Professional Guidance

Seeking guidance from a healthcare provider or a certified doula can provide personalized advice tailored to individual needs.

1. Cephalic presentation is good or bad?

Cephalic position is generally considered good as it aligns with the natural process of childbirth. It reduces the likelihood of complications and increases the chances of a successful vaginal delivery . However, it's essential to note that the overall health of both the mother and baby determines its appropriateness.

2. How to increase the chances of normal delivery in cephalic presentation?

Increasing the chances of normal delivery in cephalic presentation involves adopting healthy practices during pregnancy, such as maintaining good posture, engaging in appropriate exercises, and seeking professional guidance. However, individual circumstances vary, and consultation with a healthcare provider is paramount.

Final Thoughts

Navigating the journey of pregnancy involves understanding various aspects, and cephalic presentation plays a crucial role in determining the birthing experience. The benefits of a head-first position, coupled with strategies to encourage it, empower expectant mothers to actively participate in promoting optimal fetal positioning. As always, consulting with healthcare professionals ensures personalized care and guidance, fostering a positive and informed approach towards childbirth.

1. Makajeva J, Ashraf M. Delivery, Face and Brow Presentation. (2023). In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing

2. Boos R, Hendrik HJ, Schmidt W. (1987). Das fetale Lageverhalten in der zweiten Schwangerschaftshälfte bei Geburten aus Beckenendlage und Schädellage [Behavior of fetal position in the 2d half of pregnancy in labor with breech and vertex presentations]. Geburtshilfe Frauenheilkd

Anupama Chadha

Anupama Chadha, born and raised in Delhi is a content writer who has written extensively for industries such as HR, Healthcare, Finance, Retail and Tech.

Get baby's diet chart, and growth tips

Related Articles

100 Common Words that start with 'C' for Small Children

List of 100+ Common Words that start with 'D' for Small Children

ಗರ್ಭಧಾರಣೆಯ ಮೊದಲ 3 ತಿಂಗಳಲ್ಲಿ ಲೈಂಗಿಕತೆ: ನಿರೀಕ್ಷಿತ ದಂಪತಿಗಳಿಗೆ ಮಾಡಬೇಕಾದ ಮತ್ತು ಮಾಡಬಾರದ ಕೆಲಸಗಳು | Sex During First 3 Months of Pregnancy: Do's and Don'ts for Expecting Couples in Kannada

List of Most Common Words that start with v for small children

Related topics, labour & delivery, baby movements, tips for normal delivery, recently published articles, our most recent articles.

Diet & Nutrition

The Ultimate Guide to Consuming Chia Seeds in Pregnancy

Essential Tips for Normal Delivery After Cesarean

Crab During Pregnancy: Benefits, Risks and Smart Choices

Normal Delivery Tips: An Expecting Mother's Guide to a Smooth Childbirth Experience

Top 10 Panchatantra Stories in English You Must Read to Your Children

Health & Wellness

What Helps in Improving Mental Health of Women

• Childhood Disorders: Meaning, Symptoms & Treatment
• Bleeding During Pregnancy 8 Weeks: Should You See a Doctor?
• The Ultimate Guide to Having Sex After C Section
• The Ultimate Guide to Baby Brain Development Food During Pregnancy
• Nappy Rash: Your Ultimate Guide to Symptoms and Quick Relief
• How to Get Periods Immediately to Avoid Pregnancy?
• Loss of Appetite During Pregnancy: Causes and Solutions
• How to Increase Newborn Baby Weight: Expert Tips and Tricks
• Fertisure M: The Comprehensive Solution to Male Infertility and Reproductive Health
• All You Need to Know About the New COVID Variant: Pirola
• Endometrial Polyp and Pregnancy: How Uterine Polyps Can Affect Your Chances of Conception
• How to Stop Heavy Bleeding During Periods: Home Remedies (Part 2)
• How Many Times Should You Have Sex to Get Pregnant?
• A Guide to Planning the Perfect Godh Bharai for the Mom-to-Be

Start Exploring

• Mylo Care: Effective and science-backed personal care and wellness solutions for a joyful you.
• Mylo Baby: Science-backed, gentle and effective personal care & hygiene range for your little one.
• Mylo Community: Trusted and empathetic community of 10mn+ parents and experts.

Product Categories

baby carrier | baby soap | baby wipes | stretch marks cream | baby cream | baby shampoo | baby massage oil | baby hair oil | stretch marks oil | baby body wash | baby powder | baby lotion | diaper rash cream |

• Register-org
• Subscriptions

Recent Posts

• 9 Things to Consider When Choosing a Therapist
• Psychology Behind Online Casino Free Spins
• 10 Tips for Maintaining Oral Hygiene with Braces or Aligners
• The Stress of Academic Pressure: How Parents Can Help Teens Cope
• The Benefits of Physical Therapy for Older Adults
• Entries feed
• Comments feed
• WordPress.org
• Allergy and Immunology
• Anesthesiology
• Basic Science
• Cardiothoracic Surgery
• Cardiovascular
• Complementary Medicine
• Critical Care Medicine
• Dermatology
• Emergency Medicine
• Endocrinology, Diabetes and Metabolism
• Gastroenterology and Hepatology
• Hematology, Oncology and Palliative Medicine
• Internal Medicine
• Medical Education
• Neonatal – Perinatal Medicine
• Neurosurgery
• Nursing & Midwifery & Medical Assistant
• Obstetrics & Gynecology
• Opthalmology
• Orthopaedics
• Otolaryngology
• Physical Medicine and Rehabilitation
• Plastic Reconstructive Surgery
• Pulmolory and Respiratory
• Rheumatology

Search Engine

Normal labor, delivery, and postpartum care.

Published on 10/03/2015 by admin

Filed under Obstetrics & Gynecology

Last modified 10/03/2015

This article have been viewed 25213 times

Chapter 8 Normal Labor, Delivery, and Postpartum Care

ANATOMIC CONSIDERATIONS, OBSTETRIC ANALGESIA AND ANESTHESIA, AND RESUSCITATION OF THE NEWBORN

Calvin J. Hobel, Mark Zakowski

Labor is a process that permits a series of extensive physiologic changes in the mother to allow for the delivery of her fetus through the birth canal. It is defined as progressive cervical effacement and dilation resulting from regular uterine contractions that occur at least every 5 minutes and last 30 to 60 seconds.

The role of the obstetrician is to anticipate and manage abnormalities that may occur to either the maternal or the fetal process. When a decision is made to intervene, it must be considered carefully because each intervention carries not only potential benefits but also potential risks. In most cases, the best management may be close observation and, when necessary, cautious intervention.

Vaginal delivery necessitates the accommodation of the fetal head to the bony pelvis.

The head is the largest and least compressible part of the fetus. Thus, from an obstetric viewpoint, it is the most important part, whether the presentation is cephalic or breech.

The fetal skull consists of a base and a vault (cranium). The base of the skull has large, ossified, firmly united, and noncompressible bones. This serves to protect the vital structures contained within the brain stem.

The cranium consists of the occipital bone posteriorly, two parietal bones bilaterally, and two frontal and temporal bones anteriorly. The cranial bones at birth are thin, weakly ossified, easily compressible, and interconnected only by membranes. These features allow them to overlap under pressure and to change shape to conform to the maternal pelvis, a process known as “ molding .”

The membrane-occupied spaces between the cranial bones are known as sutures. The sagittal suture lies between the parietal bones and extends in an anteroposterior direction between the fontanelles, dividing the head into right and left sides ( Figure 8-1 ). The lambdoid suture extends from the posterior fontanelle laterally and serves to separate the occipital from the parietal bones. The coronal suture extends from the anterior fontanelle laterally and serves to separate the parietal and frontal bones. The frontal suture lies between the frontal bones and extends from the anterior fontanelle to the glabella (the prominence between the eyebrows).

FIGURE 8-1 Superior view of the fetal skull showing the sutures, fontanelles, and transverse diameters.

Fontanelles

The membrane-filled spaces located at the point where the sutures intersect are known as fontanelles, the most important of which are the anterior and posterior fontanelles Clinically, they are even more useful in diagnosing the fetal head position than the sutures.

The posterior fontanelle closes at 6 to 8 weeks of life, whereas the anterior fontanelle does not become ossified until about 18 months. This allows the skull to accommodate the tremendous growth of the infant’s brain after birth.

The anterior fontanelle ( bregma ) is found at the intersection of the sagittal, frontal, and coronal sutures. It is diamond shaped and measures about 2 × 3 cm, and it is much larger than the posterior fontanelle. The posterior fontanelle is Y- or T-shaped and is found at the junction of the sagittal and lambdoid sutures.

The fetal skull is characterized by a number of landmarks. Moving from front to back, they include the following ( Figure 8-2 ):

FIGURE 8-2 Lateral view of the fetal skull showing the prominent landmarks and the anteroposterior diameters.

Several diameters of the fetal skull are important (see Figures 8-1 and 8-2 ). The anteroposterior diameter presenting to the maternal pelvis depends on the degree of flexion or extension of the head and is important because the various diameters differ in length. The following measurements are considered average for a term fetus:

The transverse diameters of the fetal skull are as follows:

The average circumference of the term fetal head, measured in the occipitofrontal plane, is 34.5 cm.

PELVIC ANATOMY

Bony pelvis.

The bony pelvis is made up of four bones: the sacrum, coccyx, and two innominates (composed of the ilium, ischium, and pubis). These are held together by the sacroiliac joints, the symphysis pubis, and the sacrococcygeal joint. The union of the pelvis and the vertebral column stabilizes the pelvis and allows weight to be transmitted to the lower extremities.

The sacrum consists of five fused vertebrae. The anterior-superior edge of the first sacral vertebra is called the promontory, which protrudes slightly into the cavity of the pelvis. The anterior surface of the sacrum is usually concave. It articulates with the ilium at its upper segment, with the coccyx at its lower segment, and with the sacrospinous and sacrotuberous ligaments laterally.

The coccyx is composed of three to five rudimentary vertebrae. It articulates with the sacrum, forming a joint, and occasionally the bones are fused.

The pelvis is divided into the false pelvis above and the true pelvis below the linea terminalis. The false pelvis is bordered by the lumbar vertebrae posteriorly, an iliac fossa bilaterally, and the abdominal wall anteriorly. Its only obstetric function is to support the pregnant uterus.

The true pelvis is a bony canal and is formed by the sacrum and coccyx posteriorly and by the ischium and pubis laterally and anteriorly. Its internal borders are solid and relatively immobile. The posterior wall is twice the length of the anterior wall. The true pelvis is the area of concern to the obstetrician because its dimensions are sometimes not adequate to permit passage of the fetus.

Pelvic Planes

The pelvis is divided into the following four planes for descriptive purposes:

These planes are imaginary, flat surfaces that extend across the pelvis at different levels. Except for the plane of greatest diameter, each plane is clinically significant.

The plane of the inlet is bordered by the pubic crest anteriorly, the iliopectineal line of the innominate bones laterally, and the promontory of the sacrum posteriorly. The fetal head enters the pelvis through this plane in the transverse position.

The plane of greatest diameter is the largest part of the pelvic cavity. It is bordered by the posterior midpoint of the pubis anteriorly, the upper part of the obturator foramina laterally, and the junction of the 2nd and 3rd sacral vertebrae posteriorly. The fetal head rotates to the anterior position in this plane.

The plane of least diameter is the most important from a clinical standpoint because most instances of arrest of descent occur at this level. It is bordered by the lower edge of the pubis anteriorly, the ischial spines and sacrospinous ligaments laterally, and the lower sacrum posteriorly. Low transverse arrests generally occur in this plane.

The plane of the pelvic outlet is formed by two triangular planes with a common base at the level of the ischial tuberosities. The anterior triangle is bordered by the subpubic angle at the apex, the pubic rami on the sides, and the bituberous diameter at the base. The posterior triangle is bordered by the sacrococcygeal joint at its apex, the sacrotuberous ligaments on the sides, and the bituberous diameter at the base. This plane is the site of a low pelvic arrest.

Pelvic Diameters

The diameters of the pelvic planes represent the amount of space available at each level. The key measurements for assessing the capacity of the maternal pelvis include the following:

The average lengths of the diameters of each pelvic plane are listed in Table 8-1 .

TABLE 8-1 AVERAGE LENGTH OF PELVIC PLANE DIAMETERS

Pelvic Inlet

The pelvic inlet has five important diameters ( Figure 8-3 ). The anteroposterior diameter is described by one of two measurements. The true conjugate (anatomic conjugate) is the anatomic diameter and extends from the middle of the sacral promontory to the superior surface of the pubic symphysis. The obstetric conjugate represents the actual space available to the fetus and extends from the middle of the sacral promontory to the closest point on the convex posterior surface of the symphysis pubis.

FIGURE 8-3 Pelvic inlet and its diameters.

The transverse diameter is the widest distance between the iliopectineal lines. Each oblique diameter extends from the sacroiliac joint to the opposite iliopectineal eminence.

The posterior sagittal diameter extends from the anteroposterior and transverse intersection to the middle of the sacral promontory.

Plane of Greatest Diameter

The plane of greatest diameter has two noteworthy diameters. The anteroposterior diameter extends from the midpoint of the posterior surface of the pubis to the junction of the 2nd and 3rd sacral vertebrae. The transverse diameter is the widest distance between the lateral borders of the plane.

Plane of Least Diameter (Midplane)

The plane of least diameter has three important diameters. The anteroposterior diameter extends from the lower border of the pubis to the junction of the fourth and fifth sacral vertebrae. The transverse (bispinous) diameter extends between the ischial spines. The posterior sagittal diameter extends from the midpoint of the bispinous diameter to the junction of the fourth and fifth sacral vertebrae.

Pelvic Outlet

The pelvic outlet has four important diameters ( Figure 8-4 ). The anatomic anteroposterior diameter extends from the inferior margin of the pubis to the tip of the coccyx, whereas the obstetric anteroposterior diameter extends from the inferior margin of the pubis to the sacrococcygeal joint. The transverse (bituberous) diameter extends between the inner surfaces of the ischial tuberosities, and the posterior sagittal diameter extends from the middle of the transverse diameter to the sacrococcygeal joint.

FIGURE 8-4 Pelvic outlet and its diameters.

PELVIC SHAPES

Based on the general bony architecture, the pelvis may be classified into four basic types ( Figure 8-5 ).

FIGURE 8-5 The four basic pelvic types. The dotted line indicates the transverse diameter of the inlet. Note that the widest diameter of the inlet is posteriorly situated in an android or anthropoid pelvis. The gynecoid pelvis illustrates the location of the sacrosciatic notch, present in all pelvic types.

The gynecoid pelvis is the classic female type of pelvis and is found in about 50% of women. It has the following characteristics:

These features create a cylindrical shape that is spacious throughout. The fetal head generally rotates into the occipitoanterior position in this type of pelvis.

The android pelvis is the typical male type of pelvis, and it is found in less than 30% of women and has the following characteristics:

This type of pelvis has limited space at the inlet and progressively less space as one moves down the pelvis, owing to the funneling effect of the side walls, sacrum, and pubic rami. Thus, the amount of space is restricted at all levels. The fetal head is forced to be in the occipitoposterior position to conform to the narrow anterior pelvis. Arrest of descent is common at the midpelvis.

The anthropoid pelvis resembles that of the anthropoid ape. It is found in about 20% of women and has the following characteristics:

The fetal head can engage only in the anteroposterior diameter and usually does so in the occipitoposterior position because there is more space in the posterior pelvis.

Platypelloid

The platypelloid pelvis is best described as being a flattened gynecoid pelvis. It is found in only 3% of women, and it has the following characteristics:

The overall shape is that of a gentle curve throughout. The fetal head has to engage in the transverse diameter.

Engagement occurs when the widest diameter of the fetal presenting part has passed through the pelvic inlet. In cephalic presentations, the widest diameter is biparietal; in breech presentations, it is intertrochanteric.

The station of the presenting part in the pelvic canal is defined as its level above or below the plane of the ischial spines. The level of the ischial spines is assigned as “zero” station, and each centimeter above or below this level is given a minus or plus designation, respectively, for a total length of 10 cm.

In most women, the bony presenting part is at the level of the ischial spines when the head has become engaged. The fetal head usually engages with its sagittal suture in the transverse diameter of the pelvis. The head position is considered to be synclitic when the biparietal diameter is parallel to the pelvic plane and the sagittal suture is midway between the anterior and posterior planes of the pelvis. When this relationship is not present, the head is considered to be asynclitic ( Figure 8-6 ).

FIGURE 8-6 Anterior asynclitism entering the pelvis ( A ), and synclitism in the pelvis ( B ).

There is a distinct advantage to having the head engage in asynclitism in certain situations. In a synclitic presentation, the biparietal diameter entering the pelvis measures 9.5 cm; but when the parietal bones enter the pelvis in an asynclitic manner, the presenting diameter measures 8.75 cm. Therefore, asynclitism permits a larger head to enter the pelvis than would be possible in a synclitic presentation.

CLINICAL PELVIMETRY

The diameters that can be clinically evaluated can be assessed at the time of the first prenatal visit to screen for obvious pelvic contractions, although some obstetricians believe that it is better to wait until later in pregnancy when the soft tissues are more distensible and the examination is less uncomfortable and possibly more accurate.

The clinical evaluation is started by assessing the pelvic inlet. The pelvic inlet can be evaluated clinically for its anteroposterior diameter. The obstetric conjugate can be estimated from the diagonal conjugate, which is obtained on clinical examination (see Figure 8-3 ).

The diagonal conjugate is approximated by measuring from the lower border of the pubis to the sacral promontory using the tip of the second finger and the point where the base of the index finger meets the pubis ( Figure 8-7 ). The obstetric conjugate is then estimated by subtracting 1.5 to 2 cm, depending on the height and inclination of the pubis. Often the middle finger of the examining hand cannot reach the sacral promontory; thus, the obstetric conjugate is considered adequate. If the diagonal conjugate is greater than or equal to 11.5 cm, the anteroposterior diameter of the inlet is considered to be adequate.

FIGURE 8-7 Clinical estimation of the diagonal conjugate diameter of the pelvis.

The anterior surface of the sacrum is then palpated to assess its curvature. The usual shape is concave. A flat or convex shape may indicate anteroposterior constriction throughout the pelvis.

The midpelvis cannot accurately be measured clinically in either the anteroposterior or transverse diameter. A reasonable estimate of the size of the midpelvis, however, can be obtained as follows. The pelvic side walls can be assessed to determine whether they are convergent rather than having the normal, almost parallel, configuration. The ischial spines are palpated carefully to assess their prominence, and several passes are made between the spines to approximate the bispinous diameter. The length of the sacrospinous ligament is assessed by placing one finger on the ischial spine and one finger on the sacrum in the midline. The average length is 3 fingerbreadths. If the sacrospinous notch that is located lateral to the ligament can accommodate two-and-a-half fingertips, the posterior midpelvis is most likely of adequate dimensions. A short ligament suggests a forward inclination of the sacrum and a narrowed sacrospinous notch (see Figure 8–5, pg 95).

Finally, the pelvic outlet is assessed. This is done by first placing a fist between the ischial tuberosities. An 8.5-cm distance is considered an adequate transverse diameter. The posterior sagittal measurement should also be greater than 8 cm. The infrapubic angle is assessed by placing a thumb next to each inferior pubic ramus and then estimating the angle at which they meet. An angle of less than 90 degrees is associated with a contracted transverse diameter in the midplane and outlet.

Radiologic Assessment of the Pelvis

When an accurate measurement of the pelvis is indicated, nuclear magnetic resonance imaging (MRI) may be used. The advantage of MRI over x-ray or computed tomography (CT) for pelvic assessment is the lack of ionizing radiation exposure.

Indications

It should always be questioned whether the results obtained by radiologic assessment will have sufficient influence on the patient’s management to make the investigation worthwhile.

PREPARATION FOR LABOR

Before actual labor begins, a number of physiologic preparatory events usually occur.

Two or more weeks before labor, the fetal head in most primigravid women settles into the brim of the pelvis. In multigravida, this often does not occur until early in labor. Lightening may be noted by the mother as a flattening of the upper abdomen and an increased prominence of the lower abdomen.

False Labor

During the last 4 to 8 weeks of pregnancy, the uterus undergoes irregular contractions that normally are painless. Such contractions appear unpredictably and sporadically and can be rhythmic and of mild intensity. In the last month of pregnancy, these contractions may occur more frequently, sometimes every 10 to 20 minutes, and with greater intensity. These Braxton Hicks contractions are considered false labor in that they are not associated with progressive cervical dilation or effacement. They may serve a physiologic role in preparing the uterus and cervix for true labor.

Cervical Effacement

Before the onset of parturition, the cervix is frequently noted to soften as a result of increased water content and collagen lysis. Simultaneous effacement, or thinning of the cervix, occurs as it is taken up into the lower uterine segment ( Figure 8-8 B). Consequently, patients often present in early labor with a cervix that is already partially effaced. As a result of cervical effacement, the mucous plug within the cervical canal may be released. The onset of labor may thus be heralded by the passage of a small amount of blood-tinged mucus from the vagina (“bloody show”) .

FIGURE 8-8 A: The absence of cervical effacement before labor. B: Cervix being progressively taken up into the lower segment of the uterus (about 50% effaced). C: Cervix fully taken up (i.e., cervix is completely effaced).

STAGES OF LABOR

There are four stages of labor, each of which is considered separately. These stages in actuality are definitions of progress during labor, delivery, and the puerperium.

The first stage is from the onset of true labor to complete dilation of the cervix. The second stage is from complete dilation of the cervix to the birth of the baby. The third stage is from the birth of the baby to delivery of the placenta. The fourth stage is from delivery of the placenta to stabilization of the patient’s condition, usually at about 6 hours postpartum.

First Stage of Labor

The first stage of labor consists of two phases: a latent phase, during which cervical effacement and early dilation occur, and an active phase, during which more rapid cervical dilation occurs ( Figure 8-9 ). Although cervical softening and early effacement may occur before labor, during the first stage of labor, the entire cervical length is retracted into the lower uterine segment.

FIGURE 8-9 Cervical dilation and descent of the fetal head during labor. The first descent curve represents a fetus with a floating presenting part at the onset of labor, whereas the second represents a fetus with the presenting part fixed in the pelvis before labor.

(Modified from Friedman EA: Labor: Evaluation and Management, 2nd ed. East Norwalk, CT, Appleton-Century-Crofts, 1978, p 41.)

The length of the first stage may vary in relation to parity; primiparous patients generally experience a longer first stage than do multiparous patients ( Table 8-2 ). Because the latent phase may overlap considerably with the preparatory phase of labor, its duration is highly variable. It may also be influenced by other factors, such as sedation and stress. The active phase begins when the cervix is 3 to 4 cm dilated in the presence of regularly occurring uterine contractions. The minimal dilation during the active phase of the first stage is nearly the same for primiparous and multiparous women: 1 and 1.2 cm/hour, respectively. If progress is slower than this, evaluation for uterine dysfunction, fetal malposition, or cephalopelvic disproportion should be undertaken.

TABLE 8-2 CHARACTERISTICS OF NORMAL LABOR

MEASUREMENT OF PROGRESS

During the first stage, the progress of labor may be measured in terms of cervical effacement, cervical dilation, and descent of the fetal head. The clinical pattern of the uterine contractions alone is not an adequate indication of progress. After completion of cervical dilation, the second stage commences. Thereafter, only the descent, flexion, and rotation of the presenting part are available to assess the progress of labor.

CLINICAL MANAGEMENT OF THE FIRST STAGE

Certain steps should be taken in the clinical management of the patient during the first stage of labor.

MATERNAL POSITION

The mother may ambulate provided that intermittent monitoring ensures fetal well-being and the presenting part is engaged in patients with ruptured membranes. If she is lying in bed, the lateral recumbent position should be encouraged to ensure perfusion of the uteroplacental unit.

ADMINISTRATION OF FLUIDS

Because of decreased gastric emptying during labor, oral fluids are best avoided. However, fasting results in the more rapid development of ketosis in pregnant women. Placement of a 16- to 18-gauge venous catheter is advisable during the active phase of labor. Recently, it has been shown that giving at least 125 mL/hour of 10% dextrose (D) in normal saline (NS), compared with 5% D/NS or just NS, results in significantly shorter labors Thus, this intravenous route is used to both hydrate the patient with crystalloids and provide calories during labor, to administer oxytocin after the delivery of the placenta, and for the treatment of any unanticipated emergencies.

INVESTIGATIONS

Every woman admitted in labor should have a hematocrit or hemoglobin measurement and a blood clot held in the event that a crossmatch is needed. Blood group, Rhesus (Rh) type, and an antibody screen should be done if these are not known. It is also important to know the hepatitis B status of the mother so that a pediatrician can be notified if the mother is positive. Additionally, a voided urine specimen should be checked for the presence of protein and glucose.

MATERNAL MONITORING

Maternal pulse rate, blood pressure, respiratory rate, and temperature should be recorded every 1 to 2 hours in normal labor and more frequently if indicated. Fluid balance, particularly urine output and intake, should be monitored carefully.

Adequate analgesia is important during the first stage of labor (see later in this chapter).

FETAL MONITORING

The fetal heart rate should be evaluated either by auscultation with a De Lee stethoscope, by external monitoring with Doppler equipment, or by internal monitoring with a fetal scalp electrode. In uncomplicated pregnancies, continuous electronic fetal monitoring is not necessary, as several studies have demonstrated that intermittent auscultation of the fetal heart rate, when performed in conjunction with a 1:1 nurse-to-patient ratio, results in comparable outcomes. In patients with no significant obstetric risk factors, the fetal heart rate should be auscultated or the electronic monitor tracing evaluated at least every 30 minutes in the active phase of the first stage of labor and at least every 15 minutes in the second stage of labor. In patients with obstetric risk factors, the fetal heart rate should be auscultated or the electronic monitoring tracing evaluated at least every 15 minutes during the active phase of the first stage of labor (immediately following a uterine contraction), and at least every 5 minutes during the second stage.

UTERINE ACTIVITY

Uterine contractions should be monitored every 30 minutes by palpation for their frequency, duration, and intensity. For high-risk pregnancies, uterine contractions should be monitored continuously along with the fetal heart rate This can be achieved electronically using either an external tocodynamometer or an internal pressure catheter in the amniotic cavity. The latter is particularly of value when a patient’s labor is being augmented with oxytocin (Pitocin).

VAGINAL EXAMINATION

During the latent phase, particularly when the membranes are ruptured, vaginal examinations should be done sparingly to decrease the risk for an intrauterine infection. In the active phase, the cervix should be assessed about every 2 hours to determine the progress of labor.

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related posts:

Hacker & Moores Essentials of Obstetrics and Gynecology

Emergency Obstetrics and Pediatrics

2-19. limb presentation.

Transport the mother to the hospital immediately if an arm or leg is presented first. Keep the mother in the delivery position (follow local guidelines.) DO NOT attempt to deliver the baby.

CAUTION: DO NOT try to pull on the presenting limb.

DO NOT try to replace the limb into the vagina.

DO NOT place your hand into the vagina unless there is a prolapsed cord.

A Distance Learning Course