is cephalic presentation is good for normal delivery

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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.

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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.

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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.

• Learn   /  

Why Is Cephalic Presentation Ideal For Childbirth?

5   Dec   2017 | 8 min Read

During labour, contractions stretch your birth canal so that your baby has adequate room to come through during birth. The cephalic presentation is the safest and easiest way for your baby to pass through the birth canal.

If your baby is in a non-cephalic position, delivery can become more challenging. Different fetal positions pose a range of difficulties and varying risks and may not be considered ideal birthing positions.

Two Kinds of Cephalic Positions

There are two kinds of cephalic positions:

• Cephalic occiput anterior , where your baby’s head is down and is facing toward your back.
• Cephalic occiput posterior , where your baby is positioned head down, but they are facing your abdomen instead of your back. This position is also nicknamed ‘sunny-side-up’ and can increase the chances of prolonged and painful delivery. 

How to Know if Your Baby is In a Cephalic Position?

You can feel your baby’s position by rubbing your hand on your belly. If you feel your little one’s stomach in the upper stomach, then your baby is in a cephalic position. But if you feel their kicks in the lower stomach, then it could mean that your baby is in a breech position.

You can also determine whether your baby is in the anterior or posterior cephalic position. If your baby is in the anterior position, you may feel their movement underneath your ribs and your belly button could also pop out. If your baby is in the posterior position, then you may feel their kicks in their abdomen, and your stomach may appear rounded up instead of flat. 

You can also determine your baby’s position through an ultrasound scan or a physical examination at your healthcare provider’s office. 

Benefits of Cephalic Presentation in Pregnancy

Cephalic presentation is one of the most ideal birth positions, and has the following benefits:

• It is the safest way to give birth as your baby’s position is head-down and prevents the risk of any injuries.
• It can help your baby move through the delivery canal as safely and easily as possible.
• It increases the chances of smooth labour and delivery.

Are There Any Risks Involved in Cephalic Position?

Conditions like a cephalic posterior position in addition to a narrow pelvis of the mother can increase the risk of pregnancy complications during delivery. Some babies in the head-first cephalic presentation might have their heads tilted backward. This may, in some rare cases, cause preterm delivery.

What are the Risks Associated with Other Birth Positions?

A small percentage of babies may settle into a non-cephalic position before their birth. This can pose risks to both your and your baby’s health, and also influence the way in which you deliver. 

In the next section, we have discussed a few positions that your baby can settle in throughout pregnancy, as they move around the uterus. But as they grow old, there will be less space for them to tumble around, and they will settle into their final position. This is when non-cephalic positions can pose a risk.  

Breech Position

There are three types of breech fetal positioning:

• Frank breech : Your baby’s legs stick straight up along with their feet near their head.
• Footling breech: One or both of your baby’s legs are lowered over your cervix.
• Complete breech: Your baby is positioned bottom-first with their knees bent.

If your baby is in a breech position , vaginal delivery is considered complicated. When a baby is born in breech position, the largest part of their body, that is, their head is delivered last. This can lead to injury or even fetal distress. Moreover, the umbilical cord may also get damaged or get wrapped around your baby’s neck, cutting off their oxygen supply.  

If your baby is in a breech position, your healthcare provider may recommend a c-section, or they may try ways to flip your baby’s position in a cephalic presentation.

Transverse Lie

In this position, your baby settles in sideways across the uterus rather than being in a vertical position. They may be:

• Head-down, with their back facing the birth canal
• One shoulder pointing toward the birth canal
• Up with their hands and feet facing the birth canal

If your baby settles in this position, then your healthcare provider may suggest a c-section to reduce the risk of distress in your baby and other pregnancy complications.

Turning Your Baby Into A Cephalic Position

External cephalic version (ECV) is a common, and non-invasive procedure that helps turn your baby into a cephalic position while they are in the womb. However, your healthcare provider may only consider this procedure if they consider you have a stable health condition in the last trimester, and if your baby hasn’t changed their position by the 36th week.

You can also try some natural remedies to change your baby’s position, such as:

• Lying in a bridge position: Movements like bridge position can sometimes help move your baby into a more suitable position. Lie on your back with your feet flat on the ground and your legs bent. Raise your pelvis and hips into a bridge position and hold for 5-10 minutes. Repeat several times daily.
• Chiropractic care: A chiropractor can help with the adjustment of your baby’s position and also reduce stress in them.
• Acupuncture: After your doctor’s go-ahead, you can also consider acupuncture to get your baby to settle into an ideal birthing position.

While most babies settle in a cephalic presentation by the 36th week of pregnancy, some may lie in a breech or transverse position before birth. Since the cephalic position is considered the safest, your doctor may recommend certain procedures to flip your baby’s position to make your labour and delivery smooth. You may also try the natural methods that we discussed above to get your baby into a safe birthing position and prevent risks or other pregnancy complications. 

When Should A Baby Be In A Cephalic Position?

Your baby would likely naturally drop into a cephalic position between weeks 37 to 40 of your pregnancy .

Is Cephalic Position Safe?

Research shows that 95% of babies take the cephalic position a few weeks or days before their due date. It is considered to be the safest position. It ensures a smooth birthing process.

While most of the babies are in cephalic position at delivery, this is not always the case. If you have a breech baby, you can discuss the available options for delivery with your doctor.

Does cephalic presentation mean labour is near?

Head-down is the ideal position for your baby within your uterus during birth. This is known as the cephalic position. This posture allows your baby to pass through the delivery canal more easily and safely.

Can babies change from cephalic to breech?

The external cephalic version (ECV) is the most frequent procedure used for turning a breech infant.

How can I keep my baby in a cephalic position?

While your baby naturally gets into this position, you can try some exercises to ensure that they settle in cephalic presentation. Exercises such as breech tilt, forward-leaning position (spinning babies program), cat and camel pose can help.

Stitches after a normal delivery : How many stitches do you need after a vaginal delivery? Tap this post to know.

Vaginal birth after caesarean delivery : Learn all about the precautions to consider before having a vaginal delivery after a c-section procedure. 

How many c-sections can you have : Tap this post to know the total number of c-sections that you can safely have.

Cover Image Credit: Freepik.com

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Pelvimetry for fetal cephalic presentations at or near term for deciding on mode of delivery

Pelvimetry assesses the size of a woman's pelvis aiming to predict whether she will be able to give birth vaginally or not. This can be done by clinical examination, or by conventional X‐rays, computerised tomography (CT) scanning, or magnetic resonance imaging (MRI).

To assess the effects of pelvimetry (performed antenatally or intrapartum) on the method of birth, on perinatal mortality and morbidity, and on maternal morbidity. This review concentrates exclusively on women whose fetuses have a cephalic presentation.

Search methods

We searched Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2017) and reference lists of retrieved studies.

Selection criteria

Randomised controlled trials (including quasi‐randomised) assessing the use of pelvimetry versus no pelvimetry or assessing different types of pelvimetry in women with a cephalic presentation at or near term were included. Cluster trials were eligible for inclusion, but none were identified.

Data collection and analysis

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of the evidence using the GRADE approach.

Main results

Five trials with a total of 1159 women were included. All used X‐ray pelvimetry to assess the pelvis. X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that examined other types of radiological pelvimetry or that compared clinical pelvimetry versus no pelvimetry.

The included trials were generally at high risk of bias. There is an overall high risk of performance bias due to lack of blinding of women and staff. Two studies were also at high risk of selection bias. We used GRADEpro software to grade evidence for our selected outcomes; for caesarean section we rated the evidence low quality and all the other outcomes (perinatal mortality, wound sepsis, blood transfusion, scar dehiscence and admission to special care baby unit) as very low quality. Downgrading was due to risk of bias relating to lack of allocation concealment and blinding, and imprecision of effect estimates.

Women undergoing X‐ray pelvimetry were more likely to have a caesarean section (risk ratio (RR) 1.34, 95% confidence interval (CI) 1.19 to 1.52; 1159 women; 5 studies; low‐quality evidence ). There were no clear differences between groups for perinatal outcomes: perinatal mortality (RR 0.53, 95% CI 0.19 to 1.45; 1159 infants; 5 studies; very low‐quality evidence ), perinatal asphyxia (RR 0.66, 95% CI 0.39 to 1.10; 305 infants; 1 study), and admission to special care baby unit (RR 0.20, 95% CI 0.01 to 4.13; 288 infants; 1 study; very low‐quality evidence ). Other outcomes assessed were wound sepsis (RR 0.83, 95% CI 0.26 to 2.67; 288 women; 1 study; very low‐quality evidence ), blood transfusion (RR 1.00, 95% CI 0.39 to 2.59; 288 women; 1 study; very low‐quality evidence ), and scar dehiscence (RR 0.59, 95% CI 0.14 to 2.46; 390 women; 2 studies; very low‐quality evidence ). Again, no clear differences were found for these outcomes between the women who received X‐ray pelvimetry and those who did not. Apgar score less than seven at five minutes was not reported in any study.

Authors' conclusions

X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types or pelvimetry (other radiological examination or clinical pelvimetry versus no pelvimetry). There is not enough evidence to support the use of X‐ray pelvimetry for deciding on mode of delivery in women whose fetuses have a cephalic presentation. Women who undergo an X‐ray pelvimetry may be more likely to have a caesarean section.

Further research should be directed towards defining whether there are specific clinical situations in which pelvimetry can be shown to be of value. Newer methods of pelvimetry (CT, MRI) should be subjected to randomised trials to assess their value. Further trials of X‐ray pelvimetry in cephalic presentations would be of value if large enough to assess the effect on perinatal mortality.

Plain language summary

What is the issue?

Does the use of pelvimetry to assess the size of the woman's pelvis improve outcomes for baby and mother? Pelvimetry might identify babies whose heads are too big for their mother's pelvis. In this case, an elective caesarean section might improve the outcome. Forms of pelvimetry include radiological pelvimetry (X‐ray, computerised tomography (CT) scan or magnetic resonance imaging (MRI)) and clinical examination of the woman. We planned to include all studies comparing the use of clinical or radiological (X‐ray, CT or MRI) pelvimetry versus no pelvimetry, or different types of pelvimetry.

Why is this important?

Sometimes, normal labour does not progress because the baby's head is too big, or the pelvis of the mother is too small, for the baby to pass through. This is called "cephalo‐pelvic disproportion" or "obstructed labour" which may lead to an emergency caesarean section with possible risks for both mother and baby. A pregnant mother or her caregiver might be worried that disproportion could occur and for this reason, pelvimetry can be performed either before or during labour. It can be undertaken by clinical examination, X‐ray, CT‐scan or MRI. Pelvimetry measures the diameters of the pelvis and the baby's head. However, doing a pelvimetry also has implications: clinical examination might be very uncomfortable for the mother, X‐ray and CT‐scanning might be harmful for the baby and MRI is very expensive. All of these techniques have to be performed meticulously by experienced and skilled people to have any real value.

If we could diagnose the disproportion accurately before birth using pelvimetry, we might reduce the need for an emergency caesarean section and plan an elective procedure, with better outcomes for the baby and less complications for the mother.

What evidence did we find?

We searched for evidence on 30th November 2016 and identified five trials with a total of 1159 pregnant women. All five trials used X‐ray pelvimetry in comparison to no X‐ray pelvimetry.

The women who received X‐ray pelvimetry were more likely to have a caesarean section ( low‐quality evidence ). Whether a woman had pelvimetry or not, we found no difference in the numbers of babies that died ( very low‐quality evidence ), who did not have enough oxygen during labour, or were admitted to special care baby units ( very low‐quality evidence ). For the women, no differences were found between numbers of women with wound sepsis, those who received a blood transfusion, or those whose caesarean section scar began to break down ( all very low‐quality evidence ). Apgar score less than seven at five minutes was not reported in any study.

What does this mean?

There is too little evidence (the majority of which is low quality) to show whether measuring the size of the woman's pelvis (pelvimetry) is beneficial and safe when the baby is in a head‐down position. The number of women having a caesarean section increased if women had X‐ray pelvimetry but there was insufficient good‐quality evidence to show if pelvimetry improves outcomes for the baby. More research is needed.

Summary of findings

Description of the condition.

Cephalo‐pelvic disproportion (CPD) is one of the leading indications for an emergency caesarean section. CPD occurs when there is a mismatch between the fetal head and the maternal pelvis (when the fetal head is too big for the pelvis), resulting in obstructed labour.

Emergency caesarean sections have been shown to have an increased risk of maternal and neonatal morbidity and mortality ( van Ham 1997 ). Women undergoing an emergency caesarean section are at an increased risk for intra‐ and postoperative complications such as haemorrhage (tearing of the uterine incision into the parametrium or cervix, hysterotomy extension), infection (wound sepsis, endometritis), deep vein thrombosis and prolonged hospitalisation. Risks for the neonate include respiratory problems and trauma.

Women with a previous caesarean scar are known to be at risk for uterine rupture, stillbirth and placenta praevia in subsequent pregnancies. Performing a repeat caesarean section also increases the risk of bowel or bladder injury and haemorrhage and women who have had a previous caesarean section can be offered a trial of labour (vaginal birth after caesarean section (VBAC)) to reduce the intra‐ and postoperative complications of a caesarean section. However, the low but life‐threatening risk (for both mother and fetus) of a uterine rupture during labour has to be taken into consideration and explained to the woman ( Dodd 2013 ).

Description of the intervention

Assessment of the size of a woman's pelvis (pelvimetry) can be achieved by clinical examination (where the bony pelvis is digitally examined to identify prominent structures that may cause obstructed labour), or by conventional X‐rays (usually a lateral and anterior‐posterior view used to physically measure the sizes of the pelvic inlet, midpelvis and pelvic outlet, Morgan 1992 ), computerised tomography (CT) scanning (measuring the pelvis in the lateral, anterior‐posterior and axial views, Morris 1993 ), or magnetic resonance imaging (MRI, measuring of a midline sagittal, and oblique coronal views of the pelvis, Sporri 2002 ).

How the intervention might work

The aim of pelvimetry (whichever method is used) in women whose fetuses have a cephalic presentation, is to detect the presence of cephalo‐pelvic disproportion and therefore the need for caesarean section. Pelvimetry may influence clinical care since clinicians who feel that vaginal birth would be impossible, would offer the woman an elective caesarean section, thereby reducing the need of an emergency caesarean section. The criteria for determining an adequate or small pelvis have been from descriptive studies and senior opinions ( Mengert 1948 ).

Why it is important to do this review

These techniques are not without risks, the greatest of all being a false positive result and unnecessary caesarean section. Clinical pelvimetry is very uncomfortable for the woman, X‐rays and CT scanning expose the fetus to radiation (the latter slightly less so), and MRI is very expensive. All of these techniques have to be performed meticulously by experienced and skilled people in order to have any value at all.

To assess the effects of pelvimetry (performed antenatally, or intrapartum) on the method of birth, on perinatal mortality and morbidity, and on maternal morbidity. This review concentrates exclusively on women whose fetuses have a cephalic presentation.

Criteria for considering studies for this review

Types of studies

We included all randomised controlled trials (including quasi‐randomised) comparing pelvimetry in cephalic presentations versus no pelvimetry or comparing different types of pelvimetry. We would have included cluster trials if they had been identified during the search. Cross‐over studies were not eligible for this review.

If an abstract was of interest, we would have contacted the authors for further information about their trial.

Types of participants

Pregnant women with a singleton, cephalic presentation fetus who have or have not had a previous caesarean section. Studies that recruited women before, or during labour were included as well as women for spontaneous labour, induction of labour, or trial of scar after previous caesarean section (otherwise known as vaginal birth after caesarean or VBAC).

Types of interventions

The main intervention of interest is pelvimetry as a predictor of cephalo‐pelvic disproportion. Control groups could include women who did not have pelvimetry or who had different types of pelvimetry.

We planned to include studies comparing different methods of clinical or radiological pelvimetry such as X‐rays, computerised tomography (CT) scanning or magnetic resonance imaging (MRI). We reported women who have had one previous caesarean section and women who have had no previous section, or are nulliparous, in separate clinical subgroups.

Types of outcome measures

Primary outcomes, caesarean section, perinatal mortality, secondary outcomes, maternal outcomes, puerperal pyrexia, wound sepsis, blood transfusion, scar dehiscence, perinatal outcomes, perinatal asphyxia.

• Admission to special care baby units

Apgar score less than seven at five minutes

Search methods for identification of studies.

The following methods section of this review is based on a standard template used by Cochrane Pregnancy and Childbirth.

Electronic searches

We searched Cochrane Pregnancy and Childbirth’s Trials Register by contacting their Information Specialist (31 January 2017).

The Register is a database containing over 22,000 reports of controlled trials in the field of pregnancy and childbirth. For full search methods used to populate Pregnancy and Childbirth’s Trials Register including the detailed search strategies for CENTRAL, MEDLINE, Embase and CINAHL; the list of handsearched journals and conference proceedings, and the list of journals reviewed via the current awareness service, please follow this link to the editorial information about the Cochrane Pregnancy and Childbirth in the Cochrane Library and select the ‘ Specialized Register ’ section from the options on the left side of the screen.

Briefly, Cochrane Pregnancy and Childbirth’s Trials Register is maintained by their Information Specialist and contains trials identified from:

• monthly searches of the Cochrane Central Register of Controlled Trials (CENTRAL);
• weekly searches of MEDLINE (Ovid);
• weekly searches of Embase (Ovid);
• monthly searches of CINAHL (EBSCO);
• handsearches of 30 journals and the proceedings of major conferences;
• weekly current awareness alerts for a further 44 journals plus monthly BioMed Central email alerts.

Search results are screened by two people and the full text of all relevant trial reports identified through the searching activities described above is reviewed. Based on the intervention described, each trial report is assigned a number that corresponds to a specific Pregnancy and Childbirth review topic (or topics), and is then added to the Register. The Information Specialist searches the Register for each review using this topic number rather than keywords. This results in a more specific search set which has been fully accounted for in the relevant review sections ( Included studies ; Excluded studies ).

Searching other resources

We searched the reference lists of retrieved studies.

We did not apply any language or date restrictions.

For methods used in the previous version of this review, see Pattinson 1997 .

For this update, the following methods were used for assessing the two reports that were identified as a result of the updated search.

The following methods section of this review is based on a standard template used by Cochrane Pregnancy and Childbirth Group.

Selection of studies

Two review authors independently assessed for inclusion all the potential studies identified as a result of the search strategy. We resolved any disagreement through discussion or, if required, we consulted the third review author.

Data extraction and management

We designed a form to extract data. For eligible studies, two review authors extracted the data using the agreed form. We resolved discrepancies through discussion or, if required, we consulted the third review author. Data were entered into Review Manager software ( RevMan 2014 ) and checked for accuracy.

When information regarding any of the above was unclear, we planned to contact authors of the original reports to provide further details.

Assessment of risk of bias in included studies

Two review authors independently assessed risk of bias for each study using the criteria outlined in the Cochrane Handbook for Systematic Reviews of Interventions ( Higgins 2011 ). Any disagreement was resolved by discussion or by involving a third assessor.

(1) Random sequence generation (checking for possible selection bias)

We described for each included study the method used to generate the allocation sequence in sufficient detail to allow an assessment of whether it should produce comparable groups.

We assessed the method as:

• low risk of bias (any truly random process, e.g. random number table; computer random number generator);
• high risk of bias (any non‐random process, e.g. odd or even date of birth; hospital or clinic record number);
• unclear risk of bias.

(2) Allocation concealment (checking for possible selection bias)

We described for each included study the method used to conceal allocation to interventions prior to assignment and assessed whether intervention allocation could have been foreseen in advance of, or during recruitment, or changed after assignment.

We assessed the methods as:

• low risk of bias (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);
• high risk of bias (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth);

(3.1) Blinding of participants and personnel (checking for possible performance bias)

We described for each included study the methods used, if any, to blind study participants and personnel from knowledge of which intervention a participant received. We considered that studies were at low risk of bias if they were blinded, or if we judged that the lack of blinding unlikely to affect results. We assessed blinding separately for different outcomes or classes of outcomes.

• low, high or unclear risk of bias for participants;
• low, high or unclear risk of bias for personnel.

(3.2) Blinding of outcome assessment (checking for possible detection bias)

We described for each included study the methods used, if any, to blind outcome assessors from knowledge of which intervention a participant received. We assessed blinding separately for different outcomes or classes of outcomes.

We assessed methods used to blind outcome assessment as:

• low, high or unclear risk of bias.

(4) Incomplete outcome data (checking for possible attrition bias due to the amount, nature and handling of incomplete outcome data)

We described for each included study, and for each outcome or class of outcomes, the completeness of data including attrition and exclusions from the analysis. We stated whether attrition and exclusions were reported and the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information was reported, or could be supplied by the trial authors, we planned to re‐include missing data in the analyses which we undertook.

We assessed methods as:

• low risk of bias (e.g. no missing outcome data; missing outcome data balanced across groups);
• high risk of bias (e.g. numbers or reasons for missing data imbalanced across groups; ‘as treated’ analysis done with substantial departure of intervention received from that assigned at randomisation);

(5) Selective reporting (checking for reporting bias)

We described for each included study how we investigated the possibility of selective outcome reporting bias and what we found.

• low risk of bias (where it is clear that all of the study’s pre‐specified outcomes and all expected outcomes of interest to the review have been reported);
• high risk of bias (where not all the study’s pre‐specified outcomes have been reported; one or more reported primary outcomes were not pre‐specified; outcomes of interest are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported);

(6) Other bias (checking for bias due to problems not covered by (1) to (5) above)

We described for each included study any important concerns we had about other possible sources of bias.

(7) Overall risk of bias

We made explicit judgements about whether studies were at high risk of bias, according to the criteria given in the Handbook ( Higgins 2011 ). With reference to (1) to (6) above, we planned to assess the likely magnitude and direction of the bias and whether we considered it is likely to impact on the findings. In future updates, we will explore the impact of the level of bias through undertaking sensitivity analyses ‐ see Sensitivity analysis .

Assessment of the quality of the evidence using the GRADE approach

For this update the quality of the evidence was assessed using the GRADE approach as outlined in the GRADE handbook in order to assess the quality of the body of evidence relating to the following outcomes for the main comparison ‐ X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry in cephalic presentations.

We used the GRADEpro Guideline Development Tool to import data from Review Manager 5.3 ( RevMan 2014 ) in order to create a 'Summary of findings’ table. A summary of the intervention effect and a measure of quality for each of the above outcomes was produced using the GRADE approach. The GRADE approach uses five considerations (study limitations, consistency of effect, imprecision, indirectness and publication bias) to assess the quality of the body of evidence for each outcome. The evidence can be downgraded from 'high quality' by one level for serious (or by two levels for very serious) limitations, depending on assessments for risk of bias, indirectness of evidence, serious inconsistency, imprecision of effect estimates or potential publication bias.

Measures of treatment effect

Dichotomous data.

For dichotomous data, we presented results as summary risk ratio with 95% confidence intervals.

Continuous data

We did not include any continuous outcomes, however, if we do include them in future updates, we will use the mean difference if outcomes are measured in the same way between trials. We will use the standardised mean difference to combine trials that measure the same outcome, but use different methods.

Unit of analysis issues

Cluster‐randomised trials.

We did not identify any cluster‐randomised trials to include in the analyses. However, in future updates of the review, if we identify suitable cluster‐randomised trials, we will adjust their sample sizes or standard errors using the methods described in the Handbook Section 16.3.4 or 16.3.6 using an estimate of the intracluster correlation co‐efficient (ICC) derived from the trial (if possible), from a similar trial or from a study of a similar population. If we use ICCs from other sources, we will report this and conduct sensitivity analyses to investigate the effect of variation in the ICC. If we identify both cluster‐randomised trials and individually‐randomised trials, we plan to synthesise the relevant information. We will consider it reasonable to combine the results from both if there is little heterogeneity between the study designs and the interaction between the effect of intervention and the choice of randomisation unit is considered to be unlikely.

We will also acknowledge heterogeneity in the randomisation unit and perform a sensitivity or subgroup analysis to investigate the effects of the randomisation unit.

Cross‐over trials

Cross‐over trials were not eligible for this review.

Other unit of analysis issues

Multiple pregnancies.

Women with multiple pregnancies were not included in this review. If included in future updates, we will use cluster‐trial methods as described above to adjust the data. Babies from multiple pregnancies may be more likely to develop the same outcomes (non‐independence), so counting each as a separate data point may overestimate the sample size and make confidence intervals too narrow. We will regard each woman as a randomised cluster and use cluster‐trial methods to adjust outcomes for the baby.

Trials with more than two arms

If we had identified trials with more than two arms we would have pooled results using the methods set out in the Handbook (Higgins 2011) to avoid double‐counting.

Dealing with missing data

For included studies, levels of attrition were noted. In future updates, if more eligible studies are included, the impact of including studies with high levels of missing data in the overall assessment of treatment effect will be explored by using sensitivity analysis.

For all outcomes, analyses were carried out, as far as possible, on an intention‐to‐treat basis, i.e. we attempted to include all participants randomised to each group in the analyses. The denominator for each outcome in each trial was the number randomised minus any participants whose outcomes were known to be missing.

Assessment of heterogeneity

We assessed statistical heterogeneity in each meta‐analysis using the Tau², I² and Chi² statistics. We regarded heterogeneity as substantial if an I² was greater than 30% and either a Tau² was greater than zero, or there was a low P value (less than 0.10) in the Chi² test for heterogeneity. If we had identified substantial heterogeneity (above 30%), we would have explored it.

Assessment of reporting biases

In future updates, if there are 10 or more studies in the meta‐analysis, we will investigate reporting biases (such as publication bias) using funnel plots. We will assess funnel plot asymmetry visually. If asymmetry is suggested by a visual assessment, we will perform exploratory analyses to investigate it.

Data synthesis

We carried out statistical analysis using the Review Manager software ( RevMan 2014 ). We used fixed‐effect meta‐analysis for combining data where it was reasonable to assume that studies were estimating the same underlying treatment effect: i.e. where trials were examining the same intervention, and the trials’ populations and methods were judged sufficiently similar.

In future updates, if there is clinical heterogeneity sufficient to expect that the underlying treatment effects differed between trials, or if substantial statistical heterogeneity is detected, we will use random‐effects meta‐analysis to produce an overall summary, if an average treatment effect across trials is considered clinically meaningful. The random‐effects summary will be treated as the average range of possible treatment effects and we will discuss the clinical implications of treatment effects differing between trials. If the average treatment effect is not clinically meaningful, we will not combine trials. If we use random‐effects analyses, the results will be presented as the average treatment effect with 95% confidence intervals, and the estimates of Tau² and I².

Subgroup analysis and investigation of heterogeneity

We did not use subgroup analyses to investigate substantial heterogeneity. We carried out a clinical subgroup analyses on an issue of particular interest: women with no previous caesarean section versus women with previous caesarean section. This analysis was carried out for each review outcome. We assessed subgroup differences by interaction tests available within RevMan ( RevMan 2014 ). We reported the results of subgroup analyses quoting the Chi² statistic and P value, and the interaction test I² value.

Sensitivity analysis

We carried out sensitivity analyses to explore the effect of trial quality assessed by concealment of allocation with studies at high risk of allocation bias being excluded from the analyses in order to assess whether this makes any difference to the overall result. In future updates, if any trial is judged to be of poor quality due to being at high risk of bias for allocation concealment, high attrition rates, or both, we will also exclude these from the analysis.

Description of studies

Please see Characteristics of included studies and Characteristics of excluded studies for further details.

Results of the search

For this update, we assessed two reports of one trial ( Gaitan 2009 ) from a search of Cochrane Pregnancy and Childbirth's Trials Register (January 2017). In total, five trials are now included ( Crichton 1962 ; Gaitan 2009 ; Parsons 1985 ; Richards 1985 ; Thubisi 1993 ) and one is excluded ( Farrell 2002 ). See: Figure 1 .

Study flow diagram.

Included studies

Five trials with a total of 1159 women were included.

Study design

All included trials were two‐armed randomised controlled trials, using individual randomisation. Sample sizes were small and ranged from 102 ( Richards 1985 ) to 305 women ( Crichton 1962 ).

Trials were conducted in hospitals in South Africa ( Crichton 1962 ; Richards 1985 ; Thubisi 1993 ), USA ( Parsons 1985 ) and Spain ( Gaitan 2009 ).

Participants

Gaitan 2009 and Parsons 1985 only included nulliparous women in their trials, Crichton 1962 did not specify the parity of the women included, and Richards 1985 and Thubisi 1993 only included women with one previous lower segment caesarean section.

Gaitan 2009 and Parsons 1985 only randomised women who were being induced or augmented with oxytocin. Crichton 1962 randomised women when they were in labour and their doctor requested a pelvimetry. Both Richards 1985 and Thubisi 1993 performed pelvimetry at 36 weeks' gestation so women were randomised during pregnancy.

Interventions and comparisons

All of the trials included in the review examined X‐ray pelvimetry. We did not identify any trials comparing clinical pelvimetry with no pelvimetry, or examining other types of radiological pelvimetry.

Crichton 1962 included 305 women in labour whose attending doctors requested pelvimetry. Women were randomised to receive X‐ray pelvimetry or no pelvimetry during labour. No fetal heart rate monitoring was performed.

Parsons 1985 recruited 200 primigravid women who required induction of labour or augmentation of labour with oxytocin. All women received a clinical pelvimetry. Women were subsequently randomised by hospital number to either receive or not receive an X‐ray pelvimetry. Continuous fetal heart rate monitoring was done.

Richards 1985 included 102 women with one previous caesarean section (classical uterine incision being excluded). Women were randomised into two groups: the first group received an X‐ray pelvimetry at 36 weeks' gestation. If the pelvic inlet was less than 10.5 cm in the antero‐posterior diameter or less than 11.5 cm in the transverse diameter, an elective caesarean section was performed. The other women and the control group underwent a trial of scar, and had X‐ray pelvimetry postpartum as a comparison.

Thubisi 1993 randomised 288 women with one previous transverse lower segment caesarean section. The intervention group received an X‐ray pelvimetry at 36 weeks' gestation. A sagittal inlet of less than 11 cm, sagittal outlet of less than 10 cm, transverse inlet less than 11.5 cm, and transverse outlet (bispinous) less than 9 cm was an indication for caesarean section. The other women in the intervention group and the control group awaited a trial of scar.

Gaitan 2009 included 264 women. Women were randomised into two groups to either receive or not receive an X‐ray pelvimetry.

Crichton 1962 : outcomes were caesarean section/symphysiotomy, perinatal mortality, asphyxia and maternal survival.

Parsons 1985 : outcomes assessed were length of labour, length of rupture of membranes, length of oxytocin administration, type of birth, Apgar scores and birthweight.

Richards 1985 : outcomes measured were mode of birth, pelvimetry measurements, birthweight and average stay in hospital.

Thubisi 1993 : outcomes measured were caesarean section, perinatal mortality, birthweight, scar dehiscence, puerperal pyrexia, wound sepsis and blood transfusion.

Gaitan 2009 : outcomes measured were time from induction to birth of baby, method of birth, use of instruments during birth, any adverse effects and perinatal mortality.

Funding sources were not disclosed by any of the trialists.

Excluded studies

One trial was excluded: Farrell 2002 ; there were too few women recruited, study protocol was not adhered to, and the trial was stopped prior to completion due to inadequate randomisation.

Risk of bias in included studies

Please see Figure 2 and Figure 3 for a summary of 'Risk of bias' assessments.

'Risk of bias' summary: review authors' judgements about each risk of bias item for each included study.

'Risk of bias' graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

In all studies selection bias cannot be excluded, although Richards 1985 and Thubisi 1993 randomised a more homogeneous group of women as they were not in labour at the time of randomisation.

Both Crichton 1962 and Richards 1985 risk of selection bias was assessed as being 'unclear' due to not enough information being provided in the papers. Parsons 1985 and Thubisi 1993 were assessed as high risk as Parsons 1985 allocated women by hospital number, and Thubisi 1993 'randomly' assigned women at the first antenatal visit to one of two consultant teams, allocated by admitting clerks who had no medical training and knowledge of how they would be managed. Gaitan 2009 used a random number table to allocate women into groups but allocation concealment is not mentioned adequately.

Crichton 1962 relied on the attending clinician to request a pelvimetry and Parsons 1985 included a group of women requiring augmentation of labour, indicating that labour was already not progressing as expected.

None of the trials blinded participants, care givers or outcome assessors. For this type of outcome, blinded would be very difficult.

Incomplete outcome data

Thubisi 1993 randomised 306 women but only followed up 288. This loss to follow‐up is relatively low but loss of two women in the pelvimetry group related to outcomes of the study (women opted for caesarean section). For this reason, Thubisi 1993 was assessed as being at unclear risk of attrition bias. Richards 1985 was also assessed as unclear due to missing totals in the results tables of the study.

All remaining trials were assessed to be at low risk of attrition bias as data were reported for all women who were randomised.

Selective reporting

Protocols were not available for any of the included studies. Crichton 1962 , Parsons 1985 , Richards 1985 and Thubisi 1993 did not pre‐specify outcomes in the methods text. Gaitan 2009 does not report all outcomes, however in is unclear if this is due to translation issues. All trials were assessed to be at unclear risk of reporting bias.

Other potential sources of bias

All the trials were assessed to be at unclear risk of other bias except for Parsons 1985 and Thubisi 1993 who were assessed to be at low risk of bias as the baseline characteristics of both groups were similar and there was no other evidence of bias. Crichton 1962 and Richards 1985 did not report any baseline characteristics, and Gaitan 2009 had some unclear discrepancy between totals in tables and in text though it was unclear if this were due to translation issues.

Effects of interventions

See: Table 1

Summary of findings 1

1 Most studies contributing data had design limitations. Two studies had serious design limitations (high risk of bias for sequence generation and allocation concealment) one of which contributed 37.4% of weight (‐2).

2 Most studies contributing data had design limitations. (‐1)

3 Wide confidence interval crossing the line of no effect, small sample size, few events and lack of precision. (‐2)

4 One study contributing data with serious design limitations. (‐2)

5 Very wide confidence intervals crossing the line of no effect, small sample size and few events. (‐2)

6 Study contributing 79.7% total weight has serious design limitations. (‐2)

X‐ray pelvimetry versus no X‐ray pelvimetry

All five trials assessed the rate of caesarean section as an outcome, including a total of 1159 women. Crichton 1962 reported caesarean section and symphysiotomy results combined, therefore data for both caesarean section and symphysiotomy are included in this analysis. No other study reported symphysiotomy.

Women who had X‐ray pelvimetry had a higher rate of caesarean section than those women who had no X‐ray pelvimetry. The risk ratio (RR) for caesarean section is 1.34 (95% confidence interval (CI) 1.19 to 1.52; 1159 women; 5 trials; low‐quality evidence ) Analysis 1.1 when compared to women who did not get an X‐ray pelvimetry. Quality of evidence as assessed using GRADE is low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 1: Caesarean section

Subgroup interaction tests suggest no clear differences in effects for women with previous versus women with no previous caesarean section (Test for subgroup differences: Chi² = 1.52, df = 1 (P = 0.22), I² = 34.1%). The two trials that only included women with a previous section ( Richards 1985 ; Thubisi 1993 ), performed elective caesarean sections on the women whose pelvic inlets did not satisfy pre‐specified requirements following antenatal X‐ray pelvimetry; all those who did satisfy requirements were left to go into spontaneous labour. A higher caesarean rate might therefore be expected. In future updates of this review it will be useful to analyse data for rates of elective and emergency caesarean sections separately.

All five trials assessed the perinatal mortality as an outcome, including a total of 1159 women. There is no clear difference in perinatal mortality between women who did and women who did not receive an X‐ray pelvimetry (RR 0.53, 95% CI 0.19 to 1.45; 1159 infants; 5 trials; very low‐quality evidence ) Analysis 1.2 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 2: Perinatal mortality

One trial including 288 women who all had a previous caesarean ( Thubisi 1993 ) assessed the incidence of puerperal pyrexia as an outcome after caesarean in both groups (women who did receive an X‐ray pelvimetry compared to women who did not). Little difference was found: RR 0.80 (95% CI 0.22 to 2.92; 288 women; 1 trial) Analysis 1.3 .

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 3: Puerperal pyrexia

One trial including 288 women ( Thubisi 1993 ) assessed the incidence of wound sepsis as an outcome after caesarean in both groups (women who did receive an X‐ray pelvimetry compared to women who did not). Little difference was found: RR 0.83 (95% CI 0.26 to 2.67; 288 women; 1 trial; very low‐quality evidence ) Analysis 1.4 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 4: Wound sepsis

One trial including 288 women ( Thubisi 1993 ) assessed the need for blood transfusion as an outcome in both groups (women who did receive an X‐ray pelvimetry compared to women who did not). No difference was found: RR 1.00 (95% CI 0.39 to 2.59; 288 women; 1 trial; very low‐quality evidence ) Analysis 1.5 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 5: Blood transfusion

Two trials including 390 women ( Richards 1985 ; Thubisi 1993 ) assessed the incidence of scar dehiscence as an outcome in women who had one previous transverse uterine segment caesarean section and underwent trial of scar. Little difference was found: RR 0.59 (95% CI 0.14 to 2.46; 390 women; 2 trials; v ery low‐quality evidence ) Analysis 1.6 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 6: Scar dehiscence

One trial including 305 infants ( Crichton 1962 ) assessed incidence of perinatal asphyxia. Little difference was found: RR 0.66 (95% CI 0.39 to 1.10; 305 infants; 1 trial) Analysis 1.7 .

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 7: Perinatal asphyxia

Admission to special care baby unit

One trial including 288 infants ( Thubisi 1993 ) assessed the need for admission to a special care baby unit. Little difference was found: RR 0.20 (95% CI 0.01 to 4.13; 288 infants; 1 trial; very low‐quality evidence ) Analysis 1.8 . Quality of evidence as assessed using GRADE is very low.

Comparison 1: X‐ray pelvimetry versus no X‐ray pelvimetry, Outcome 8: Admission to special care baby units

No trials assessed the Apgar score less than seven at five minutes as an outcome.

Women without previous caesarean section

Three trials included women with no previous caesarean section ( Crichton 1962 ; Gaitan 2009 ; Parsons 1985 ) with a total number of 769 women. There is a higher caesarean section rate (and symphysiotomy rate in Crichton 1962 ) in the X‐ray pelvimetry group (RR 1.24, 95% CI 1.02 to 1.52; 769 women; 3 trials). There is no difference in perinatal mortality (RR 0.64, 95% CI 0.21 to 1.90; 769 women; 3 trials). There was a slight decrease in perinatal asphyxia and perinatal mortality in Crichton 1962 , but this decrease in perinatal mortality was not observed in Parsons 1985 or Gaitan 2009 . Neither trial reported perinatal asphyxia. The decrease seen in Crichton 1962 could be due to chance or lack in fetal monitoring. None of these trials reported puerperal pyrexia, wound sepsis, blood transfusion, or admission to special care baby unit. Scar dehiscence was not relevant to these women.

Women with previous caesarean section

Two trials included women who had a previous transverse lower segment caesarean section ( Richards 1985 ; Thubisi 1993 ), with a total number of 390 women. There was an overall increase in the caesarean section rate in both studies in the X‐ray pelvimetry groups (RR 1.45, 95% CI 1.26 to 1.67; 390 women; 2 trials). There was a slight decrease in perinatal mortality, which could have occurred by chance, in Richards 1985 , but this was not observed in Thubisi 1993 where there were no perinatal deaths in either group (RR 0.19, 95% CI 0.01 to 3.91; 390 women; 2 trials). There were similar rates of scar dehiscence in the intervention and control groups (RR 0.59, 95% CI 0.14 to 2.46; 390 women; 2 trials). Thubisi 1993 reported a slight increase in admissions to special care baby units in the control group, but again these could have occurred by chance. Richards 1985 did not report this outcome. Only Thubisi 1993 reported puerperal pyrexia, wound sepsis and blood transfusion and did not find any difference between the groups.

We carried out sensitivity analysis for lack of allocation concealment. Parsons 1985 and Thubisi 1993 were assessed to be at high risk of selection bias and were removed from Analysis 1.1 : Caesarean section/symphysiotomy and Analysis 1.2 : Perinatal mortality. There were not sufficient data to remove these trials from the other outcomes and maintain a meaningful analysis.

For the outcome caesarean section/symphysiotomy, removing the trial data widened the CIs and lessened the effect slightly (RR 1.25, 95% CI 1.04 to 1.49), but the data still showed that women who had pelvimetry were more likely to have a caesarean section. Regarding the women without a previous caesarean section, removing Parsons 1985 meant that the CIs crossed the line of no effect (RR 1.19, 95% CI 0.96 to 1.47).

There were no perinatal deaths in either Parsons 1985 or Thubisi 1993 , so removing the data from the meta‐analysis made no difference to the overall relative risk.

X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types of pelvimetry (other radiological examination).

Summary of main results

Five trials with a total of 1159 women were included. All used X‐ray pelvimetry to assess the pelvis. X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types or pelvimetry.

Women who received an X‐ray pelvimetry, had a higher risk having a caesarean section, without a decrease in perinatal mortality. The control groups tended to a slightly raised perinatal mortality, but this could be due to chance. The numbers studied were insufficient to assess perinatal mortality adequately. No clear differences were found between groups for puerperal pyrexia, wound sepsis, blood transfusion, scar dehiscence, perinatal asphyxia or admission to special care baby unit. No trial reported Apgar score less than seven at five minutes.

Parsons 1985 explains the increased perinatal mortality and asphyxia in Crichton 1962 by the lack of electronic fetal monitoring available to the women in Crichton's trial. The two deaths in the study of Richards 1985 occurred in utero before the onset of labour.

Some of the outcomes in this review, relating to women with a previous caesarean, are difficult to interpret because they are mediated by another outcome, for example, wound sepsis and blood transfusion are only relevant to those women who have a caesarean section.

Overall completeness and applicability of evidence

The trials are compatible with respect to the common measures of outcome. The small number of trials included in this review address the research question and do not support the use of X‐ray pelvimetry, though they are of low quality, and there are no trials to assess the use of computed tomography (CT) or magnetic resonance imaging (MRI) pelvimetry. The paucity of trials assessing the effectiveness of all methods of pelvimetry, for both women with and without a previous caesarean, limits the applicability of this review. The majority of the few trials available are over 20 years old. This perhaps reflects how little pelvimetry is used by clinicians in current practice.

The trials were also conducted in a small number of countries (South Africa, Spain, and the USA) and therefore the findings may not be applicable to low‐income settings.

Quality of the evidence

All trial designs regarding treatment allocation were of poor quality, assessed as high or unclear risk of bias. None of the trials blinded participants, staff or outcome assessors. The trials were not well‐reported so it was difficult to assess the other 'Risk of bias' domains. The two trials in women with previous caesarean sections were performed at the same institution a few years apart. We have found that overall, the findings are at a moderate to high risk of bias. Please see Figure 2 for a summary of the risk of bias.

We used GRADEpro software to grade evidence for our selected outcomes; for caesarean section we rated the evidence low quality and all the other outcomes, perinatal mortality, wound sepsis, blood transfusion, scar dehiscence and admission to special care baby unit as very low quality. Downgrading was due to risk of bias relating to lack of allocation concealment and blinding, and imprecision of effect estimates. Please see Table 1 .

Potential biases in the review process

We took steps to reduce bias as we are aware of the potential to introduce bias throughout the process of writing the review. Two review authors assessed each study for possible inclusion, assessed the quality of the trials and extracted data independently. We recognise that assessing the quality of the trials can be subjective and that different people assessing risk of bias may have come up with different judgements.

Agreements and disagreements with other studies or reviews

The results of this review agree with another non‐Cochrane systematic review that looked at clinical interventions, including X‐ray pelvimetry, which increased vaginal birth after caesarean section (VBAC) ( Catling‐Paull 2011 ). Catling‐Paull 2011 found that X‐ray pelvimetry was a poor predictor of birth outcome, and that women who received pelvimetry were less likely to attempt a vaginal birth. Subsequently, the caesarean section rate was higher in the groups where women had pelvimetry.

Implications for practice

X‐ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types or pelvimetry (e.g. other radiological examinations). There is not enough evidence to support the use of X‐ray pelvimetry for deciding on the mode of delivery in women whose fetuses have a cephalic presentation, and the practice may be harmful to the mother by increasing the risk of having a caesarean section, without increasing the benefit to the fetus or neonate.

Implications for research

Further research should be directed towards defining whether there are specific clinical situations, for example, breech presentations, in which X‐ray pelvimetry can be shown to be of value. Newer methods of pelvimetry should be subjected to randomised trials to assess their value.

Further trials of X‐ray pelvimetry in cephalic presentations would be of value if large enough to assess the effect on perinatal mortality.

Anthony Todd, December 2020

It occurred to me that, having been involved with dogs with large heads and tiny pelvices that a simple measurement of the widest part of the pelvis may be related to the chances of dystocia. A basic measurement at any stage of pregnancy. or before. may predict with some, not all, as exceptions in nature are the rule, accuracy the chances of dystocia. these women could therefore be identified and prepared [in all sorts of ways] for the likelihood of dystocia.

Protocol first published: Issue 2, 1997 Review first published: Issue 2, 1997

Acknowledgements

Professor Justus Hofmeyr and Ms Cheryl Nikodem for assisting me with the study and teaching me (V Vannevel) the use of Review Manager. Thanks to Therese Dowswell (Cochrane Pregnancy and Childbirth) for her contribution in assessing studies and help preparing the 'Summary of findings' table for this update (2016).

This research was supported by a grant from the Department of Reproductive Health and Research, World Health Organization (WHO). The findings, interpretations and conclusions expressed in this paper are entirely those of the authors and should not be attributed in any manner whatsoever to WHO.

We thank El‐Marie Farrell for contributions to the previous update.

As part of the pre‐publication editorial process, this review has been commented on by three peers (an editor and two referees who are external to the editorial team), a member of Cochrane Pregnancy and Childbirth's international panel of consumers and the Group's Statistical Adviser.

This project was supported by the National Institute for Health Research, via Cochrane Infrastructure funding to Cochrane Pregnancy and Childbirth. The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, NHS or the Department of Health.

Edited (no change to conclusions)

Data and analyses

Comparison 1, characteristics of studies, characteristics of included studies [ordered by study id], characteristics of excluded studies [ordered by study id], differences between protocol and review.

Title: We changed the title from Pelvimetry for fetal cephalic presentations at or near term to Pelvimetry for fetal cephalic presentations at or near term for deciding on mode of delivery .

Objectives: We removed assessing the effects of postnatal pelvimetry from the objectives as this could not impact on mode of delivery.

We also removed the following hypothesis.

• Information provided by pelvimetry in women without previous caesarean section is useful because it decreases the morbidity and mortality in the women and fetuses or neonates.
• Information provided by pelvimetry in women with previous caesarean section is useful because it decreases the morbidity and mortality in the women and fetuses or neonates.

We have clarified aspects in the section on Criteria for considering studies for this review, as follows:

All acceptably randomised comparisons of the use of pelvimetry in cephalic presentations in:

• women without previous caesarean section;
• women with previous caesarean section.

has changed to:

• Women without caesarean section;
• Women with previous caesarean section.

Pregnant women with singleton, cephalic presentation fetus who have or have not had a previous caesarean section. Studies which recruited women before, or during labour were included as well as women for spontaneous labour, induction or trial of scar after previous caesarean section.

Policy of elective caesarean section or trial of labour or scar depending on the prediction of pelvimetry as opposed to trial of labour or scar in all.

Outcomes: We changed ' Caesarean section/symphysiotomy' to ' Caesarean section'. Crichton 1962 only, reported the composite outcome of caesarean section/symphysiotomy, and did not report data for these outcomes separately. It is not clear how many symphysiotomies were performed in this trial and we could not report the data as two separate outcomes. We have documented this in the results section and in footnotes in Analysis 1.1 .

'Summary of findings' table: We assessed the trial quality by using GRADE assessment. This is documented in Table 1 .

Contributions of authors

V Vannevel assisted RC Pattinson with the 2016 update. V Vannevel analysed and interpreted the results, and prepared the update. A Cuthbert assessed studies for inclusion and prepared the 'Summary of findings' table.

Sources of support

Internal sources.

• University of Pretoria, South Africa

External sources

• South African Medical Research Council, South Africa
• Department of Reproductive Health and Research, World Health Organization, Switzerland
• UNDP‐UNFPA‐UNICEF‐WHO‐World Bank Special Programme of Research, Development and Research Training in Human Reproduction (HRP), Department of Reproductive Health and Research (RHR), World Health Organization, Switzerland

Declarations of interest

Robert C Pattinson: no conflict of interest. Anna Cuthbert: no conflict of interest. Valerie Vannevel: no conflict of interest.

References to studies included in this review

Crichton 1962 {published data only}.

• Crichton D. The accuracy and value of cephalopelvimetry . Journal of Obstetrics and Gynaecology of the British Commonwealth 1962; 69 :366-78. [ Google Scholar ]

Gaitan 2009 {published data only}

• Gaitan N, Duenas JL, Bedoya C, Taboada C, Polo J. Prospective, randomised and controlled study to evaluate the usefulness of radiopelvimetry in induced labour in primigravidae [Estudio prospectivo, aleatorizado y controlado para evaluar la utilidad de la radiopelvimetria en la induccion de parto en primigravidas]. Progresos de Obstetricia y Ginecologia 2009; 52 ( 10 ):552-6. [ Google Scholar ]
• Gaitan Quintero N, Duenas Diez JL, Bedoya Bergua C, Taboada Montes C, Padillo JP. The use of the radiopelvimetria previously to the induction of labor in primigravidas . Journal of Maternal-Fetal and Neonatal Medicine 2010; 23 ( S1 ):278. [ Google Scholar ]

Parsons 1985 {published data only}

• Parsons MT, Spellacy WN. Prospective randomised study of X-ray pelvimetry in the primigravida . Obstetrics & Gynecology 1985; 66 :76-9. [ PubMed ] [ Google Scholar ]

Richards 1985 {published data only}

• Richards A, Strang A, Moodley J, Philpott H. Vaginal delivery following caesarean section - is X-ray pelvimetry a reliable predictor? In: Proceedings of 4th Conference on Priorities in Perinatal Care in South Africa, 1985; Natal, South Africa . 1985:62-5.

Thubisi 1993 {published data only}

• Thubisi M, Ebrahim A, Moodley J, Shweni PM. Vaginal delivery after previous caesarean section: is X-ray pelvimetry necessary? British Journal of Obstetrics and Gynaecology 1993; 100 :421-4. [ PubMed ] [ Google Scholar ]

References to studies excluded from this review

Farrell 2002 {unpublished data only}.

• Volschenk S, Farrell E, Jeffery BS, Pattinson RC. Clinical pelvimetry as a predictor of vaginal delivery in women with one previous caesarean section . In: 20th Conference on Priorities in Perinatal Care in Southern Africa; 2001 March 6-9; KwaZulu-Natal, South Africa . 2002.

Additional references

Catling‐paull 2011.

• Catling-Paull C, Johnston R, Ryan C, Foureur MJ, Homer CSE. Clinical interventions that increase the uptake and success of vaginal birth after caesarean section: a systematic review . Journal of Advanced Nursing 2011; 67 ( 8 ):1646-61. [ PubMed ] [ Google Scholar ]
• Dodd JM, Crowther CA, Huertas E, Guise JM, Horey D. Planned elective repeat caesarean section versus planned vaginal birth for women with a previous caesarean birth . Cochrane Database of Systematic Reviews 2013, Issue 12 . Art. No: CD004224. [DOI: 10.1002/14651858.CD004224.pub3] [ PubMed ] [ CrossRef ] [ Google Scholar ]

Higgins 2011

• Higgins JPT, Green S, editors. Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011 . Available from www.cochrane-handbook.org .

Mengert 1948

• Mengert WF. Estimation of pelvic capacity . JAMA 1948; 138 :169-74. [ PubMed ] [ Google Scholar ]

Morgan 1992

• Morgan MA, Thurnau GR. Efficacy of the fetal-pelvic index in nulliparous women at high risk for fetal-pelvic disproportion . American Journal of Obstetrics and Gynecology 1992; 166 ( 3 ):810-4. [ PubMed ] [ Google Scholar ]

Morris 1993

• Morris CW, Heggie JCP, Acton CM. Computed tomography pelvimetry: accuracy and radiation dose compared with conventional pelvimetry . Australasian Radiology 1993; 37 :186-91. [ PubMed ] [ Google Scholar ]

RevMan 2014 [Computer program]

• The Nordic Cochrane Centre, The Cochrane Collaboration Review Manager (RevMan) . Version 5.3. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014.

Sporri 2002

• Sporri S, Thoeny HC, Raio L, Lachat R, Vock P, Schneider H. MR imaging pelvimetry: a useful adjunct in the treatment of women at risk for dystocia? American Journal of Roentgenology 2002; 179 :137-44. [ PubMed ] [ Google Scholar ]

van Ham 1997

• Ham MAEC, Dongen PWJ, Mulder J. Maternal consequences of caesarean section - A retrospective study of intra-operative and postoperative maternal complications of caesarean section during a 10-year period . European Journal of Obstetrics & Gynecology and Reproductive Biology 1997; 74 :1-6. [ PubMed ] [ Google Scholar ]

References to other published versions of this review

Pattinson 1997.

• Pattinson RC, Farrell EME. Pelvimetry for fetal cephalic presentations at or near term . Cochrane Database of Systematic Reviews 1997, Issue 2 . Art. No: CD000161. [DOI: 10.1002/14651858.CD000161] [ PubMed ] [ CrossRef ] [ Google Scholar ]

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Your baby in the birth canal

During labor and delivery, your baby must pass through your pelvic bones to reach the vaginal opening. The goal is to find the easiest way out. Certain body positions give the baby a smaller shape, which makes it easier for your baby to get through this tight passage.

The best position for the baby to pass through the pelvis is with the head down and the body facing toward the mother's back. This position is called occiput anterior.

Information

Certain terms are used to describe your baby's position and movement through the birth canal.

FETAL STATION

Fetal station refers to where the presenting part is in your pelvis.

• The presenting part. The presenting part is the part of the baby that leads the way through the birth canal. Most often, it is the baby's head, but it can be a shoulder, the buttocks, or the feet.
• Ischial spines. These are bone points on the mother's pelvis. Normally the ischial spines are the narrowest part of the pelvis.
• 0 station. This is when the baby's head is even with the ischial spines. The baby is said to be "engaged" when the largest part of the head has entered the pelvis.
• If the presenting part lies above the ischial spines, the station is reported as a negative number from -1 to -5.

In first-time moms, the baby's head may engage by 36 weeks into the pregnancy. However, engagement may happen later in the pregnancy, or even during labor.

This refers to how the baby's spine lines up with the mother's spine. Your baby's spine is between their head and tailbone.

Your baby will most often settle into a position in the pelvis before labor begins.

• If your baby's spine runs in the same direction (parallel) as your spine, the baby is said to be in a longitudinal lie. Nearly all babies are in a longitudinal lie.
• If the baby is sideways (at a 90-degree angle to your spine), the baby is said to be in a transverse lie.

FETAL ATTITUDE

The fetal attitude describes the position of the parts of your baby's body.

The normal fetal attitude is commonly called the fetal position.

• The head is tucked down to the chest.
• The arms and legs are drawn in towards the center of the chest.

Abnormal fetal attitudes include a head that is tilted back, so the brow or the face presents first. Other body parts may be positioned behind the back. When this happens, the presenting part will be larger as it passes through the pelvis. This makes delivery more difficult.

DELIVERY PRESENTATION

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

The best position for your baby inside your uterus at the time of delivery is head down. This is called cephalic presentation.

• This position makes it easier and safer for your baby to pass through the birth canal. Cephalic presentation occurs in about 97% of deliveries.
• There are different types of cephalic presentation, which depend on the position of the baby's limbs and head (fetal attitude).

If your baby is in any position other than head down, your doctor may recommend a cesarean delivery.

Breech presentation is when the baby's bottom is down. Breech presentation occurs about 3% of the time. There are a few types of breech:

• A complete breech is when the buttocks present first and both the hips and knees are flexed.
• A frank breech is when the hips are flexed so the legs are straight and completely drawn up toward the chest.
• Other breech positions occur when either the feet or knees present first.

The shoulder, arm, or trunk may present first if the fetus is in a transverse lie. This type of presentation occurs less than 1% of the time. Transverse lie is more common when you deliver before your due date, or have twins or triplets.

CARDINAL MOVEMENTS OF LABOR

As your baby passes through the birth canal, the baby's head will change positions. These changes are needed for your baby to fit and move through your pelvis. These movements of your baby's head are called cardinal movements of labor.

• This is when the widest part of your baby's head has entered the pelvis.
• Engagement tells your health care provider that your pelvis is large enough to allow the baby's head to move down (descend).
• This is when your baby's head moves down (descends) further through your pelvis.
• Most often, descent occurs during labor, either as the cervix dilates or after you begin pushing.
• During descent, the baby's head is flexed down so that the chin touches the chest.
• With the chin tucked, it is easier for the baby's head to pass through the pelvis.

Internal Rotation

• As your baby's head descends further, the head will most often rotate so the back of the head is just below your pubic bone. This helps the head fit the shape of your pelvis.
• Usually, the baby will be face down toward your spine.
• Sometimes, the baby will rotate so it faces up toward the pubic bone.
• As your baby's head rotates, extends, or flexes during labor, the body will stay in position with one shoulder down toward your spine and one shoulder up toward your belly.
• As your baby reaches the opening of the vagina, usually the back of the head is in contact with your pubic bone.
• At this point, the birth canal curves upward, and the baby's head must extend back. It rotates under and around the pubic bone.

External Rotation

• As the baby's head is delivered, it will rotate a quarter turn to be in line with the body.
• After the head is delivered, the top shoulder is delivered under the pubic bone.
• After the shoulder, the rest of the body is usually delivered without a problem.

Alternative Names

Shoulder presentation; Malpresentations; Breech birth; Cephalic presentation; Fetal lie; Fetal attitude; Fetal descent; Fetal station; Cardinal movements; Labor-birth canal; Delivery-birth canal

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.

Kilpatrick SJ, Garrison E, Fairbrother E. Normal labor and delivery. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies . 8th ed. Philadelphia, PA: Elsevier; 2021:chap 11.

Review Date 11/10/2022

Updated by: John D. Jacobson, MD, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. 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

• Childbirth Problems

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

• Key Points |

Abnormal fetal lie or presentation may occur due to fetal size, fetal anomalies, uterine structural abnormalities, multiple gestation, or other factors. Diagnosis is by examination or ultrasonography. Management is with physical maneuvers to reposition the fetus, operative vaginal delivery , or cesarean delivery .

Terms that describe the fetus in relation to the uterus, cervix, and maternal pelvis are

Fetal presentation: Fetal part that overlies the maternal pelvic inlet; vertex (cephalic), face, brow, breech, shoulder, funic (umbilical cord), or compound (more than one part, eg, shoulder and hand)

Fetal position: Relation of the presenting part to an anatomic axis; for transverse presentation, occiput anterior, occiput posterior, occiput transverse

Fetal lie: Relation of the fetus to the long axis of the uterus; longitudinal, oblique, or transverse

Normal fetal lie is longitudinal, normal presentation is vertex, and occiput anterior is the most common position.

Abnormal fetal lie, presentation, or position may occur with

Fetopelvic disproportion (fetus too large for the pelvic inlet)

Fetal congenital anomalies

Uterine structural abnormalities (eg, fibroids, synechiae)

Multiple gestation

Several common types of abnormal lie or presentation are discussed here.

Transverse lie

Fetal position is transverse, with the fetal long axis oblique or perpendicular rather than parallel to the maternal long axis. Transverse lie is often accompanied by shoulder presentation, which requires cesarean delivery.

Breech presentation

There are several types of breech presentation.

Frank breech: The fetal hips are flexed, and the knees extended (pike position).

Complete breech: The fetus seems to be sitting with hips and knees flexed.

Single or double footling presentation: One or both legs are completely extended and present before the buttocks.

Types of breech presentations

Breech presentation makes delivery difficult ,primarily because the presenting part is a poor dilating wedge. Having a poor dilating wedge can lead to incomplete cervical dilation, because the presenting part is narrower than the head that follows. The head, which is the part with the largest diameter, can then be trapped during delivery.

Additionally, the trapped fetal head can compress the umbilical cord if the fetal umbilicus is visible at the introitus, particularly in primiparas whose pelvic tissues have not been dilated by previous deliveries. Umbilical cord compression may cause fetal hypoxemia.

Predisposing factors for breech presentation include

Preterm labor

Uterine abnormalities

Fetal anomalies

If delivery is vaginal, breech presentation may increase risk of

Umbilical cord prolapse

Birth trauma

Perinatal death

Face or brow presentation

In face presentation, the head is hyperextended, and position is designated by the position of the chin (mentum). When the chin is posterior, the head is less likely to rotate and less likely to deliver vaginally, necessitating cesarean delivery.

Brow presentation usually converts spontaneously to vertex or face presentation.

Occiput posterior position

The most common abnormal position is occiput posterior.

The fetal neck is usually somewhat deflexed; thus, a larger diameter of the head must pass through the pelvis.

Progress may arrest in the second phase of labor. Operative vaginal delivery or cesarean delivery is often required.

Position and Presentation of the Fetus

If a fetus is in the occiput posterior position, operative vaginal delivery or cesarean delivery is often required.

In breech presentation, the presenting part is a poor dilating wedge, which can cause the head to be trapped during delivery, often compressing the umbilical cord.

For breech presentation, usually do cesarean delivery at 39 weeks or during labor, but external cephalic version is sometimes successful before labor, usually at 37 or 38 weeks.

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Pelvimetry for fetal cephalic presentations at or near term for deciding on mode of delivery

What is the issue?

Does the use of pelvimetry to assess the size of the woman's pelvis improve outcomes for baby and mother? Pelvimetry might identify babies whose heads are too big for their mother's pelvis. In this case, an elective caesarean section might improve the outcome. Forms of pelvimetry include radiological pelvimetry (X-ray, computerised tomography (CT) scan or magnetic resonance imaging (MRI)) and clinical examination of the woman. We planned to include all studies comparing the use of clinical or radiological (X-ray, CT or MRI) pelvimetry versus no pelvimetry, or different types of pelvimetry.

Why is this important?

Sometimes, normal labour does not progress because the baby's head is too big, or the pelvis of the mother is too small, for the baby to pass through. This is called "cephalo-pelvic disproportion" or "obstructed labour" which may lead to an emergency caesarean section with possible risks for both mother and baby. A pregnant mother or her caregiver might be worried that disproportion could occur and for this reason, pelvimetry can be performed either before or during labour. It can be undertaken by clinical examination, X-ray, CT-scan or MRI. Pelvimetry measures the diameters of the pelvis and the baby's head. However, doing a pelvimetry also has implications: clinical examination might be very uncomfortable for the mother, X-ray and CT-scanning might be harmful for the baby and MRI is very expensive. All of these techniques have to be performed meticulously by experienced and skilled people to have any real value.

If we could diagnose the disproportion accurately before birth using pelvimetry, we might reduce the need for an emergency caesarean section and plan an elective procedure, with better outcomes for the baby and less complications for the mother.

What evidence did we find?

We searched for evidence on 30th November 2016 and identified five trials with a total of 1159 pregnant women. All five trials used X-ray pelvimetry in comparison to no X-ray pelvimetry.

The women who received X-ray pelvimetry were more likely to have a caesarean section ( low-quality evidence ). Whether a woman had pelvimetry or not, we found no difference in the numbers of babies that died ( very low-quality evidence ), who did not have enough oxygen during labour, or were admitted to special care baby units ( very low-quality evidence ). For the women, no differences were found between numbers of women with wound sepsis, those who received a blood transfusion, or those whose caesarean section scar began to break down ( all very low-quality evidence ). Apgar score less than seven at five minutes was not reported in any study.

What does this mean?

There is too little evidence (the majority of which is low quality) to show whether measuring the size of the woman's pelvis (pelvimetry) is beneficial and safe when the baby is in a head-down position. The number of women having a caesarean section increased if women had X-ray pelvimetry but there was insufficient good-quality evidence to show if pelvimetry improves outcomes for the baby. More research is needed.

X-ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that used other types or pelvimetry (other radiological examination or clinical pelvimetry versus no pelvimetry). There is not enough evidence to support the use of X-ray pelvimetry for deciding on mode of delivery in women whose fetuses have a cephalic presentation. Women who undergo an X-ray pelvimetry may be more likely to have a caesarean section.

Further research should be directed towards defining whether there are specific clinical situations in which pelvimetry can be shown to be of value. Newer methods of pelvimetry (CT, MRI) should be subjected to randomised trials to assess their value. Further trials of X-ray pelvimetry in cephalic presentations would be of value if large enough to assess the effect on perinatal mortality.

Pelvimetry assesses the size of a woman's pelvis aiming to predict whether she will be able to give birth vaginally or not. This can be done by clinical examination, or by conventional X-rays, computerised tomography (CT) scanning, or magnetic resonance imaging (MRI).

To assess the effects of pelvimetry (performed antenatally or intrapartum) on the method of birth, on perinatal mortality and morbidity, and on maternal morbidity. This review concentrates exclusively on women whose fetuses have a cephalic presentation.

We searched Cochrane Pregnancy and Childbirth Group's Trials Register (31 January 2017) and reference lists of retrieved studies.

Randomised controlled trials (including quasi-randomised) assessing the use of pelvimetry versus no pelvimetry or assessing different types of pelvimetry in women with a cephalic presentation at or near term were included. Cluster trials were eligible for inclusion, but none were identified.

Two review authors independently assessed trials for inclusion and risk of bias, extracted data and checked them for accuracy. We assessed the quality of the evidence using the GRADE approach.

Five trials with a total of 1159 women were included. All used X-ray pelvimetry to assess the pelvis. X-ray pelvimetry versus no pelvimetry or clinical pelvimetry is the only comparison included in this review due to the lack of trials identified that examined other types of radiological pelvimetry or that compared clinical pelvimetry versus no pelvimetry.

The included trials were generally at high risk of bias. There is an overall high risk of performance bias due to lack of blinding of women and staff. Two studies were also at high risk of selection bias. We used GRADEpro software to grade evidence for our selected outcomes; for caesarean section we rated the evidence low quality and all the other outcomes (perinatal mortality, wound sepsis, blood transfusion, scar dehiscence and admission to special care baby unit) as very low quality. Downgrading was due to risk of bias relating to lack of allocation concealment and blinding, and imprecision of effect estimates.

Women undergoing X-ray pelvimetry were more likely to have a caesarean section (risk ratio (RR) 1.34, 95% confidence interval (CI) 1.19 to 1.52; 1159 women; 5 studies; low-quality evidence ). There were no clear differences between groups for perinatal outcomes: perinatal mortality (RR 0.53, 95% CI 0.19 to 1.45; 1159 infants; 5 studies; very low-quality evidence ), perinatal asphyxia (RR 0.66, 95% CI 0.39 to 1.10; 305 infants; 1 study), and admission to special care baby unit (RR 0.20, 95% CI 0.01 to 4.13; 288 infants; 1 study; very low-quality evidence ). Other outcomes assessed were wound sepsis (RR 0.83, 95% CI 0.26 to 2.67; 288 women; 1 study; very low-quality evidence ), blood transfusion (RR 1.00, 95% CI 0.39 to 2.59; 288 women; 1 study; very low-quality evidence ), and scar dehiscence (RR 0.59, 95% CI 0.14 to 2.46; 390 women; 2 studies; very low-quality evidence ). Again, no clear differences were found for these outcomes between the women who received X-ray pelvimetry and those who did not. Apgar score less than seven at five minutes was not reported in any study.