what does fetal presentation mean

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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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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 vertex 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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Obstetric and Newborn Care I

10.02 key terms related to fetal positions.

a. “Lie” of an Infant.

Lie refers to the position of the spinal column of the fetus in relation to the spinal column of the mother. There are two types of lie, longitudinal and transverse. Longitudinal indicates that the baby is lying lengthwise in the uterus, with its head or buttocks down. Transverse indicates that the baby is lying crosswise in the uterus.

b. Presentation/Presenting Part.

Presentation refers to that part of the fetus that is coming through (or attempting to come through) the pelvis first.

(1) Types of presentations (see figure 10-1). The vertex or cephalic (head), breech, and shoulder are the three types of presentations. In vertex or cephalic, the head comes down first. In breech, the feet or buttocks comes down first, and last–in shoulder, the arm or shoulder comes down first. This is usually referred to as a transverse lie.

(2) Percentages of presentations.

(a) Head first is the most common-96 percent.

(b) Breech is the next most common-3.5 percent.

(c) Shoulder or arm is the least common-5 percent.

(3) Specific presentation may be evaluated by several ways.

(a) Abdominal palpation-this is not always accurate.

(b) Vaginal exam–this may give a good indication but not infallible.

(c) Ultrasound–this confirms assumptions made by previous methods.

(d) X-ray–this confirms the presentation, but is used only as a last resort due to possible harm to the fetus as a result of exposure to radiation.

c. Attitude.

This is the degree of flexion of the fetus body parts (body, head, and extremities) to each other. Flexion is resistance to the descent of the fetus down the birth canal, which causes the head to flex or bend so that the chin approaches the chest.

(1) Types of attitude (see figure 10-2).

(a) Complete flexion. This is normal attitude in cephalic presentation. With cephalic, there is complete flexion at the head when the fetus “chin is on his chest.” This allows the smallest cephalic diameter to enter the pelvis, which gives the fewest mechanical problems with descent and delivery.

(b) Moderate flexion or military attitude. In cephalic presentation, the fetus head is only partially flexed or not flexed. It gives the appearance of a military person at attention. A larger diameter of the head would be coming through the passageway.

(c) Poor flexion or marked extension. In reference to the fetus head, it is extended or bent backwards. This would be called a brow presentation. It is difficult to deliver because the widest diameter of the head enters the pelvis first. This type of cephalic presentation may require a C/Section if the attitude cannot be changed.

(d) Hyperextended. In reference to the cephalic position, the fetus head is extended all the way back. This allows a face or chin to present first in the pelvis. If there is adequate room in the pelvis, the fetus may be delivered vaginally.

(2) Areas to look at for flexion.

(a) Head-discussed in previous paragraph, 10-2c(1).

(b) Thighs-flexed on the abdomen.

(c) Knees-flexed at the knee joints.

(d) Arches of the feet-rested on the anterior surface of the legs.

(e) Arms-crossed over the thorax.

(3) Attitude of general flexion. This is when all of the above areas are flexed appropriately as described.

d. Station.

This refers to the depth that the presenting part has descended into the pelvis in relation to the ischial spines of the mother’s pelvis. Measurement of the station is as follows:

(1) The degree of advancement of the presenting part through the pelvis is measured in centimeters.

(2) The ischial spines is the dividing line between plus and minus stations.

(3) Above the ischial spines is referred to as -1 to -5, the numbers going higher as the presenting part gets higher in the pelvis (see figure10-3).

(4) The ischial spines is zero (0) station.

(5) Below the ischial spines is referred to +1 to +5, indicating the lower the presenting part advances.

e. Engagement.

This refers to the entrance of the presenting part of the fetus into the true pelvis or the largest diameter of the presenting part into the true pelvis. In relation to the head, the fetus is said to be engaged when it reaches the midpelvis or at a zero (0) station. Once the fetus is engaged, it (fetus) does not go back up. Prior to engagement occurring, the fetus is said to be “floating” or ballottable.

f. Position.

This is the relationship between a predetermined point of reference or direction on the presenting part of the fetus to the pelvis of the mother.

(1) The maternal pelvis is divided into quadrants.

(a) Right and left side, viewed as the mother would.

(b) Anterior and posterior. This is a line cutting the pelvis in the middle from side to side. The top half is anterior and the bottom half is posterior.

(c) The quadrants never change, but sometimes it is confusing because the student or physician’s viewpoint changes.

NOTE: Remember that when you are describing the quadrants, view them as the mother would.

(2) Specific points on the fetus.

(a) Cephalic or head presentation.

1 Occiput (O). This refers to the Y sutures on the top of the head.

2 Brow or fronto (F). This refers to the diamond sutures or anterior fontanel on the head.

3 Face or chin presentation (M). This refers to the mentum or chin.

(b) Breech or butt presentation.

1 Sacrum or coccyx (S). This is the point of reference.

2 Breech birth is associated with a higher perinatal mortality.

(c) Shoulder presentation.

1 This would be seen with a transverse lie.

2. Scapula (Sc) or its upper tip, the acromion (A) would be used for the point of reference.

(3) Coding of positions.

(a) Coding simplifies explaining the various positions.

1 The first letter of the code tells which side of the pelvis the fetus reference point is on (R for right, L for left).

2 The second letter tells what reference point on the fetus is being used (Occiput-O, Fronto-F, Mentum-M, Breech-S, Shoulder-Sc or A).

3 The last letter tells which half of the pelvis the reference point is in (anterior-A, posterior-P, transverse or in the middle-T).

(b) Each presenting part has the possibility of six positions. They are normally recognized for each position–using “occiput” as the reference point.

1 Left occiput anterior (LOA).

2 Left occiput posterior (LOP).

3 Left occiput transverse (LOT).

4 Right occiput anterior (ROA).

5. Right occiput posterior (ROP).

6 Right occiput transverse (ROT).

(c) A transverse position does not use a first letter and is not the same as a transverse lie or presentation.

1 Occiput at sacrum (O.S.) or occiput at posterior (O.P.).

2 Occiput at pubis (O.P.) or occiput at anterior (O.A.).

(4) Types of breech presentations (see figure10-4).

(a) Complete or full breech. This involves flexion of the fetus legs. It looks like the fetus is sitting in a tailor fashion. The buttocks and feet appear at the vaginal opening almost simultaneously.

A–Complete. B–Frank. C–Incomplete.

(b) Frank and single breech. The fetus thighs are flexed on his abdomen. His legs are against his trunk and feet are in his face (foot-in-mouth posture). This is the most common and easiest breech presentation to deliver.

(c) Incomplete breech. The fetus feet or knees will appear first. His feet are labeled single or double footing, depending on whether 1 or 2 feet appear first.

(5) Observations about positions (see figure 10-5).

(a) LOA and ROA positions are the most common and permit relatively easy delivery.

(b) LOP and ROP positions usually indicate labor may be longer and harder, and the mother will experience severe backache.

(c) Knowing positions will help you to identify where to look for FHT’s.

1 Breech. This will be upper R or L quad, above the umbilicus.

2 Vertex. This will be lower R or L quad, below the umbilicus.

(d) An occiput in the posterior quadrant means that you will feel lumpy fetal parts, arms and legs (see figure 10-5 A). If delivered in that position, the infant will come out looking up.

(e) An occiput in the anterior quadrant means that you will feel a more smooth back (see figure 10-5 B). If delivered in that position, the infant will come out looking down at the floor.

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Fetal Presentation: Baby’s First Pose

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Occiput Anterior

Occiput posterior, transverse position, complete breech, frank breech, changing fetal presentation, baby positions.

The position in which your baby develops is called the “fetal presentation.” During most of your pregnancy, the baby will be curled up in a ball – that’s why we call it the “fetal position.” The baby might flip around over the course of development, which is why you can sometimes feel a foot poking into your side or an elbow prodding your bellybutton. As you get closer to delivery, the baby will change positions and move lower in your uterus in preparation. Over the last part of your pregnancy, your doctor or medical care provider will monitor the baby’s position to keep an eye out for any potential problems.

In the occiput anterior position, the baby is pointed headfirst toward the birth canal and is facing down – toward your back. This is the easiest possible position for delivery because it allows the crown of the baby’s head to pass through first, followed by the shoulders and the rest of the body. The crown of the head is the narrowest part, so it can lead the way for the rest of the head.

The baby’s head will move slowly downward as you get closer to delivery until it “engages” with your pelvis. At that point, the baby’s head will fit snugly and won’t be able to wobble around. That’s exactly where you want to be just before labor. The occiput anterior position causes the least stress on your little one and the easiest labor for you.

In the occiput posterior position, the baby is pointed headfirst toward the birth canal but is facing upward, toward your stomach. This can trap the baby’s head under your pubic bone, making it harder to get out through the birth canal. In most cases, a baby in the occiput posterior position will either turn around naturally during the course of labor or your doctor or midwife may help it along manually or with forceps.

In a transverse position, the baby is sideways across the birth canal rather than head- or feet-first. It’s rare for a baby to stay in this position all the way up to delivery, but your doctor may attempt to gently push on your abdomen until the baby is in a more favorable fetal presentation. If you go into labor while the baby is in a transverse position, your medical care provider will likely recommend a c-section to avoid stressing or injuring the baby.

Breech Presentation

If the baby’s legs or buttocks are leading the way instead of the head, it’s called a breech presentation. It’s much harder to deliver in this position – the baby’s limbs are unlikely to line up all in the right direction and the birth canal likely won’t be stretched enough to allow the head to pass. Breech presentation used to be extremely dangerous for mothers and children both, and it’s still not easy, but medical intervention can help.

Sometimes, the baby will turn around and you’ll be able to deliver vaginally. Most healthcare providers, however, recommend a cesarean section for all breech babies because of the risks of serious injury to both mother and child in a breech vaginal delivery.

A complete breech position refers to the baby being upside down for delivery – feet first and head up. The baby’s legs are folded up and the feet are near the buttocks.

In a frank breech position, the baby’s legs are extended and the baby’s buttocks are closest to the birth canal. This is the most common breech presentation .

By late in your pregnancy, your baby can already move around – you’re probably feeling those kicks! Unfortunately, your little one doesn’t necessarily know how to aim for the birth canal. If the baby isn’t in the occiput anterior position by about 32 weeks, your doctor or midwife will typically recommend trying adjust the fetal presentation. They’ll use monitors to keep an eye on the baby and watch for signs of stress as they push and lift on your belly to coax your little one into the right spot. Your doctor may also advise you to try certain exercises at home to encourage the baby to move into the proper position. For example, getting on your hands and knees for a few minutes every day can help bring the baby around. You can also put cushions on your chairs to make sure your hips are always elevated, which can help move things into the right place. It’s important to start working on the proper fetal position early, as it becomes much harder to adjust after about 37 weeks when there’s less room to move around.

In many cases, the baby will eventually line up properly before delivery. Sometimes, however, the baby is still in the wrong spot by the time you go into labor. Your doctor or midwife may be able to move the baby during labor using forceps or ventouse . If that’s not possible, it’s generally safer for you and the baby if you deliver by c-section.

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Presentation and position of baby through pregnancy and at birth

9-minute read

If you are concerned about your baby’s movements, contact your doctor or midwife for advice immediately.

• If you baby is in a breech presentation, your doctor may recommend trying a technique called an external cephalic version to try and move your baby while they are still in the uterus for an easier birth.

What does presentation and position mean?

Presentation refers to the part of your baby’s body that is facing downwards in the direction of the birth canal.

Position refers to where your baby’s occiput (the bottom part of the back of their head) is in relation to your body.

If your baby is in a breech presentation , then position refers to where your baby’s sacrum (lower back) is in relation to your body.

People — including medical professionals — sometimes use these terms incorrectly. Sometimes when speaking about babies in breech presentation, the word ‘position’ will be used to refer to their presentation. For example, you may read information or hear people say ‘breech position’ instead of ‘breech presentation’.

What are the different types of presentation my baby could be in during pregnancy and birth?

Most babies present headfirst, also known as cephalic presentation. Most babies that are headfirst will be vertex presentation. This means that the crown of their head sits at the opening of your birth canal.

In rare cases, your baby can be headfirst but in face or brow presentation, which may not be suitable for vaginal birth.

If your baby is in a breech presentation, their feet or bottom will be closest to your birth canal. The 3 most common types of breech presentation are:

• frank or extended breech — where your baby’s legs are straight up in front of their body, with their feet up near their face
• complete or flexed breech — where your baby is in a sitting position with their legs crossed in front of their body and their feet near their bottom
• footling breech — where one or both of your baby’s feet are hanging below their bottom, so the foot or feet are coming first

Read more on breech presentation .

What are the different positions my baby could be in during pregnancy and birth?

If your baby is headfirst, the 3 main types of presentation are:

• anterior – when the back of your baby’s head is at the front of your belly
• lateral – when the back of your baby’s head is facing your side
• posterior – when the back of your baby’s head is towards your back

How will I know what presentation and position my baby is in?

Your doctor or midwife can usually work out your baby’s presentation by feeling your abdomen. They may also double check it with a portable ultrasound. Your baby’s presentation is usually checked around 36 weeks .

Your doctor or midwife will also confirm your baby’s head position in labour by examining your belly and using an ultrasound , and they may also do a vaginal examination . During the vaginal examination they are feeling for certain ridges on your baby’s head called sutures and fontanelles that help them work out which way your baby is positioned.

What is the ideal presentation and position for baby to be in for a vaginal birth?

For a vaginal birth, your baby will ideally be headfirst with the back of their head at the front of your belly, also known as being in the anterior position. This position is best for labour and birth since it means that the smallest part of your baby’s head goes down the birth canal first.

When does a baby usually get in the ideal presentation and position for birth?

Your baby will usually be in a headfirst position by 37 weeks of pregnancy. Around 3 in every 100 babies will be in breech presentation after 37 weeks.

Your baby’s position can change with your contractions during labour as they move down the birth canal, so their exact position can change during labour.

What are my options if baby isn't in the ideal presentation or position for a vaginal birth?

If your baby is in a breech presentation, your doctor may recommend a technique called an external cephalic version (ECV) to try and move your baby while they are still in the uterus . An ECV involves your doctor using their hands to apply pressure on your belly and help turn your baby to a headfirst position. It has a 1 in 2 chance of success and is a safe option in most pregnancies.

There is no evidence to show that alternative therapies, such as exercises, acupuncture or chiropractic treatments, help your baby change from a breech presentation to headfirst.

If your baby remains breech, your doctor may discuss having a breech vaginal birth. Not all doctors and hospitals offer this option. They may also suggest you birth your baby with a planned caesarean section .

If your baby’s presentation is headfirst but the position of your baby’s head is not ideal for labour, it can lead to a longer labour, and potential complications . The position of your baby’s head will often change as your labour progresses. If it doesn’t, sometimes you can still give birth without assistance, or you may need your doctor to help turn your baby’s head or help your birth with a vacuum or forceps .

Any procedure or decision for a type of birth will only go ahead with your consent . You will be able to discuss all the options with your doctor, and based on your preferences for yourself and your baby’s safety, make a decision together .

Resources and support

The Royal Australian and New Zealand College of Obstetrics and Gynaecology has a factsheet about the options available to you if your baby is in a breech presentation at the end of your pregnancy .

Mercy Perinatal has information on external cephalic version (ECV) safety and benefits if your baby is in a breech presentation at the end of your pregnancy.

The Women’s Hospital has information about the different presentations and positions your baby could be in, and how it can affect your birthing experience.

Speak to a maternal child health nurse

Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 or video call . Available 7am to midnight (AET), 7 days a week.

Learn more here about the development and quality assurance of healthdirect content .

Last reviewed: October 2023

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External Cephalic Version for Breech Presentation - Pregnancy and the first five years

This information brochure provides information about an External Cephalic Version (ECV) for breech presentation

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When a baby is positioned bottom-down late in pregnancy, this is called the breech position. Find out about 3 main types and safe birthing options.

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Malpresentation is when your baby is in an unusual position as the birth approaches. It may be possible to move the baby, but a caesarean may be safer.

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Why would posterior position matter in labor?  The head is angled so that it measures larger. The top of the head molds less than the crown.

Baby’s spine is extended, not curled, so the crown of the head is not leading the way. Baby can’t help as much during the birth process to the same degree as the curled up baby.

Some posteriors are easy, while others are long and painful, and there are several ways to tell how your labor will be beforehand. After this, you may want to visit What to do when….in Labor .

Belly Mapping ® Method tips:  The Right side of the abdomen is almost always firmer, but the direct OP baby may not favor one side or the other. Baby’s limbs are felt in front, on both sides of the center line. A knee may slide past under the navel. 

The OP position (occiput posterior fetal position) is when the back of the baby’s head is against the mother’s back. Here are drawings of an anterior and posterior presentation.

• When is Breech an Issue?
• Belly Mapping® Breech
• Flip a Breech
• When Baby Flips Head Down
• Breech & Bicornuate Uterus
• Breech for Providers
• What if My Breech Baby Doesn't Turn?
• Belly Mapping ®️ Method
• After Baby Turns
• Head Down is Not Enough
• Sideways/Transverse
• Asynclitism
• Oblique Lie
• Left Occiput Transverse
• Right Occiput Anterior
• Right Occiput Posterior
• Right Occiput Transverse
• Face Presentation
• Left Occiput Anterior
• OP Truths & Myths
• Anterior Placenta
• Body Balancing

Look at the above drawing. The posterior baby’s back is often extended straight or arched along the mother’s spine. Having the baby’s back extended often pushes the baby’s chin up.

Attention: Having the chin up is what makes the posterior baby’s head seem larger than the same baby when it’s in the anterior position.

Because the top of the head enters (or tries to enter) the pelvis first, baby seems much bigger by the mother’s measurements. A posterior head circumference measures larger than the anterior head circumference.

A large baby is not the same issue, however. The challenge with a posterior labor is that the top of the head, not the crown of the head leads the way.

A baby with their spine straight has less ability to wiggle and so the person giving birth has to do the work of two. This can be long and challenging or fast and furious. Also, there are a few posterior labors that are not perceived different than a labor with a baby curled on the left.

Why? Anatomy makes the difference. Learn to work with birth anatomy to reduce the challenge of posterior labor by preparing with our Three Balances SM and more.

What to do?

• Three Balances SM
• Dip the Hip
• Psoas Release
• Almost everything on this website except Breech Tilt

In Labor, do the above and add,

• Abdominal Lift and Tuck
• Other positions to Open the Brim
• Open the Outlet during pushing

There are four posterior positions

The direct OP is the classic posterior position with the baby facing straight forward.   Right Occiput Transverse   (ROT) is a common starting position in which the baby has a bit more likelihood of rotating to the posterior during labor than to the anterior.   Right Occiput Posterior   usually involves a straight back with a lifted chin (in the first-time mother). Left Occiput Posterior places the baby’s back opposite the maternal liver and may let the baby flex (curl) his or her back and therefore tuck the chin for a better birth. These are generalities, of course. See a bit more about posterior positions in   Belly Mapping ® on this website. Want to map your baby’s position? Learn how with the   Belly Mapping ® Workbook .

Pregnancy may or may not show symptoms.   Just because a woman’s back doesn’t hurt in pregnancy doesn’t mean the baby is not posterior. Just because a woman is quite comfortable in pregnancy doesn’t mean the baby is not posterior. A woman can’t always feel the baby’s limbs moving in front to tell if the baby is facing the front.

The four posterior fetal positions

Four starting positions often lead to (or remain as) direct   OP   in active labor.   Right Occiput Transverse   (ROT),   Right Occiput Posterior   (ROP), and Left Occiput Posterior (LOP) join direct OP in adding labor time. The LOP baby has less distance to travel to get into an LOT position.

As labor begins, the high-riding, unengaged Right Occiput Transverse baby slowly rotates to   ROA , working past the sacral promontory at the base of the spine before swinging around to LOT to engage in the pelvis. Most babies go on to OA at the pelvic floor or further down on the perineal floor.

If a baby engages as a ROT, they may go to OP or ROA by the time they descend to the midpelvis. The OP baby may stay OP. For some, once the head is lower than the bones and the head is visible at the perineum, the baby rotates and helpers may see the baby’s head turn then! These babies finish in the ROA or OA positions.

Feeling both hands in front, in two separate but low places on the abdomen, indicates a posterior fetal position. This baby is Left Occiput Posterior.

Studies estimate 15-30% of babies are OP in labor. Jean Sutton in   Optimal Fetal Positioning   states that 50% of babies trend toward posterior in early labor upon admission to the hospital. Strong latent labor swings about a third of these to LOT before dilation begins (in “pre-labor” or “false labor”).

Recent research shows about 50% of babies are in a posterior position when active labor begins, but of these, 3/4 of them rotate to anterior (or facing a hip in an occiput transverse, head down position.

Jean Sutton’s observations, reported in her 1996 book, indicates that some babies starting in a posterior position will rotate before arriving to the hospital. Ellice Lieberman observed most posteriors will rotate out of posterior into either anterior or to facing a hip throughout labor. Only 5-8% of all babies emerge directly OP (13% with an epidural in Lieberman’s study). At least 12% of all   cesareans   are for OP babies that are stuck due to the larger diameter of the OP head in comparison to the OA head. It’s more common for ROT, ROP, and OP babies to rotate during labor and to emerge facing back (OA). Some babies become stuck halfway through a long-arc rotation and some will need a cesarean anyway.

The three anterior starting positions for labor

Why not ROA? ROA babies may have their chins up and this deflexed position may lengthen the course of labor. Less than 4% of starting positions are ROA, according to a Birmingham study. This might not be ideal for first babies, but is not a posterior position either.  

The spectrum of ease across posterior labors

Purchase Parent Class

Baby’s posterior position may matter in labor

With a posterior presentation, labor may or may not be significantly affected. There is a spectrum of possibilities with a posterior baby. Some women will not know they had a posterior baby because no one mentions it. Either the providers didn’t know, or didn’t notice. If labor moved along, they may not have looked at fetal position clues since there was no reason to figure out why labor wasn’t progressing. If a woman didn’t have back labor (more pain in her back than in her abdomen), the provider may not have been “clued into” baby’s position.

Some posterior babies are born in less than 8 hours and position did not slow down labor. Some posterior babies are born in less than 24 hours and position did not slow down labor enough to be out of the norm. Some posterior babies are born in less than 36-48 hours without the need for interventions.

Some posterior labors are manageable when women are mobile, supported, and eat and drink freely, as needed. Some posterior labor needs extra support that a well-trained and experienced doula may provide, but that typically a mate or loved one would not have the skills or stamina to keep up with. Some posterior labors progress only with the help of a highly-trained pregnancy bodyworker or deep spiritual, or otherwise a non-conventional model of care. Or, they seem only able to finish with medical intervention.

Some posterior labors are served by an epidural, meaning the pelvic floor relaxes enough for the baby to rotate and come out. Some epidurals, on the other hand, make it so that a woman can not finish the birth vaginally.

NOTE:   Parents should know — some birth researchers, like Pediatrician John Kennell, are seriously asking whether a mother’s epidural turns off her body’s release of pain-relieving hormones which a baby relies on during childbirth. Some babies can’t turn and can’t be born vaginally and must be born by   cesarean. This is a spectrum of possibilities. I’ve seen every one of the above possibilities several times and can add the wonderful experience of seeing a woman laughing pleasurably and squatting while her posterior baby slid out on to her bedroom floor.

Possible posterior effects, some women will have one or two and some will have many of these:

• Longer pregnancy (some research shows this and some doesn’t)
• The amniotic sac breaking (water breaks, membranes open, rupture of membranes) before labor (1 in 5 OP labors)
• Not starting in time before induction   is scheduled
• Labor is longer and stronger and less rhythmic than expected
• Start and stop   labor pattern
• The baby may not engage, even during the pushing stage
• Longer early labor
• Longer active labor
• Back labor (in some cases)
• Pitocin may be used when labor stalls (but a snoring good rest followed by oatmeal may restore a contraction pattern, too)
• Longer pushing stage
• Maybe a woman has all three phases of labor lengthened by the OP labor or one or two of the three phases listed
• Sometimes the baby’s head gets stuck turned halfway to anterior – in the transverse diameter. This may be called a transverse arrest (not a   transverse lie ).
• More likely to tear
• More likely to need a vacuum (ventouse) or forceps
• More likely to need a   cesarean

These effects are in comparison to a baby in the   left occiput anterior   or   left occiput transverse   fetal position at the start of labor.

Who might have a hard time with a posterior baby?

• A first-time mom
• A first-time mom whose   baby hasn’t dropped into the pelvis by 38 weeks gestation   (two weeks before the due date)
• A woman with an   android pelvis   (“runs like a boy,” often long and lanky, low pubis with narrow pubic arch and/or sitz bones close together, closer than or equal to the width of a fist)
• A woman whose baby, in the third trimester, doesn’t seem to change position at all, over the weeks. He or she kicks in the womb and stretches, but whose trunk is stationary for weeks. This mother’s broad ligament may be so tight that she may be uncomfortable when baby moves.
• A woman who has an epidural early in labor (data supports this), before the baby has a chance to rotate and come down.
• A woman who labors lying in bed
• Low-thyroid, low-energy woman who has gone overdue (this is my observation)
• A woman who lacks support by a calm and assured woman who is calming and reassuring to the birthing mother (a doula)
• A woman put on the clock
• A woman who refuses all help when the labor exceeds her ability to physically sustain her self (spilling ketones, dehydration, unable to eat or rest in a labor over X amount of hours which might be 24 for some or 48 for others)
• A woman whose birth team can’t match an appropriate technique to the needs of the baby for flexion, rotation, and/or descent from the level of the pelvis where the baby is currently at when stuck

Who is likely to have an easy time with a posterior baby?

• A second-time mom who’s given birth readily before (and pushing went well)
• A posterior baby with a tucked chin on his or her mama’s left side with   a round pelvic brim
• An average-sized or smaller baby
• Someone whose posterior baby changes from right to left after doing inversions and other   balancing work , though the baby is still posterior
• A woman with a baby in the Left Occiput Posterior, especially if the baby’s chin is tucked or flexed
• A woman who gets bodywork, myofascial release, etc.
• A woman whose posterior baby engages, and does not have an   android (triangular) pelvis or a small outlet
• And of all of these, what is necessary is a pelvis big enough to accommodate the baby’s extra head size
• A woman who uses active birthing techniques — vertical positions, moves spontaneously and instinctively or with specific techniques from Spinning Babies ® , and other good advice
• A woman in a balanced nervous state, not so alert and “pumped up,” on guard, etc.

Any woman may also have an easier time than public opinion might indicate, too, just because she isn’t on this list. Equally, just because she is on the “hard” list doesn’t mean she will have a hard time for sure. These are general observations. They are neither condemnations nor promises. Overall, some posterior babies will need help getting born, while some posterior babies are born easily (easy being a relative term).

Let’s not be ideological about posterior labors.

While most posterior babies do eventually rotate, that can still mean there is quite a long wait – and a lot of physical labor during that wait. Sometimes it means the doula, midwife, nurse, or doctor is asking the mother to do a variety of position changes, techniques, and even medical interventions to help finish the labor. Patience works for many, but for some a   cesarean   is really the only way to be born. Read   What To Do When…in Labor .

What causes a baby to be posterior?

There is a rising incidence of posterior babies at the time of birth. We know now that epidural anesthesia increases the rate of posterior position at the time of birth from about 4% (for women who don’t choose an epidural in a university birth setting) up to about 13% (Lieberman, 2005). Low thyroid function is associated with fetal malposition such as posterior or breech. (See   Research & References .)

Most babies who are posterior early in labor will rotate to anterior once labor gets going. Some babies rotate late in labor, even just before emerging. Studies such as Lieberman’s show that at any given phase of labor, another 20% of posterior babies will rotate so that only a small number are still posterior as the head emerges.

My observations are that the majority of babies are posterior before labor. The high numbers of posterior babies at the end of pregnancy and in the early phase of labor is a change from what was seen in studies over ten years old. Perhaps this is from our cultural habits of sitting at desks, sitting in bucket seats (cars), and leaning back on the couch (slouching). Soft tissues such as the psoas muscle pair or the broad ligament also seem to be tight more often from these postures, from athletics (quick stops, jolts, and falls), from accidents, and from emotional or sexual assault.

Being a nurse or bodyworker who turns to care for people in a bed or on a table will also twist the lower uterine segment (along with some of the previously mentioned causes). This makes the baby have to compensate in a womb that is no longer symmetrical. Less often, the growing baby settles face-forward over a smaller pelvis, or a triangular-shaped pelvis (android). At the end of pregnancy, the baby’s forehead has settled onto a narrower than usual pubic bone, and if tight round ligaments hold the forehead there, the baby may have a tough time rotating. These are the moms and babies that I’m most concerned with in my work at Spinning Babies®. A baby that was   breech   beyond week 30 – 34 of pregnancy will flip head down in the posterior position. A woman with a history of breech or posterior babies is more likely to have a breech or posterior baby in the next pregnancy. However, she may not have an as long labor.

The best way to tell if your baby is OP or not, usually, is if you feel little wiggles in the abdomen right above your pubic bone. These are the fingers. They’d feel like little fingers wiggling, not like a big thunk or grinding from the head, though you might feel that, too. The little fingers will be playing by the mouth. This is the easiest indication of OP. The wiggles will be centered in the middle of your lower abdomen, close to the pubic bone. If you feel wiggles far to the right, near your hip, and kicks above on the right, but not near the center and none on the left, then those signal an   OA   or   LOT   baby (who will rotate to the OA easily in an active birth). After this, you might go to   What to do when…in Labor.

Check out our current references in the   Research & References   section.

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

StatPearls [Internet].

Delivery, face and brow presentation.

Julija Makajeva ; Mohsina Ashraf .

Affiliations

Last Update: January 9, 2023 .

• Continuing Education Activity

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

• Identify the mechanism of labor in the face and brow presentation.
• Differentiate potential maternal and fetal complications during the face and brow presentations.
• Evaluate different management approaches for the face and brow presentation.
• Introduction

The term presentation describes the leading part of the fetus or the anatomical structure closest to the maternal pelvic inlet during labor. The presentation can roughly be divided into the following classifications: cephalic, breech, shoulder, and compound. Cephalic presentation is the most common and can be further subclassified as vertex, sinciput, brow, face, and chin. The most common presentation in term labor is the vertex, where the fetal neck is flexed to the chin, minimizing the head circumference. Face presentation is an abnormal form of cephalic presentation where the presenting part is the mentum. This typically occurs because of hyperextension of the neck and the occiput touching the fetal back. Incidence of face presentation is rare, accounting for approximately 1 in 600 of all presentations. [1] [2] [3]  In brow presentation, the neck is not extended as much as in face presentation, and the leading part is the area between the anterior fontanelle and the orbital ridges. Brow presentation is considered the rarest of all malpresentation, with a prevalence of 1 in 500 to 1 in 4000 deliveries. [3]

Both face and brow presentations occur due to extension of the fetal neck instead of flexion; therefore, conditions that would lead to hyperextension or prevent flexion of the fetal neck can all contribute to face or brow presentation. These risk factors may be related to either the mother or the fetus. Maternal risk factors are preterm delivery, contracted maternal pelvis, platypelloid pelvis, multiparity, previous cesarean section, and black race. Fetal risk factors include anencephaly, multiple loops of cord around the neck, masses of the neck, macrosomia, and polyhydramnios. [2] [4] [5]  These malpresentations are usually diagnosed during the second stage of labor when performing a digital examination. Palpating orbital ridges, nose, malar eminences, mentum, mouth, gums, and chin in face presentation is possible. Based on the position of the chin, face presentation can be further divided into mentum anterior, posterior, or transverse. In brow presentation, the anterior fontanelle and face can be palpated except for the mouth and the chin. Brow presentation can then be further described based on the position of the anterior fontanelle as frontal anterior, posterior, or transverse. Diagnosing the exact presentation can be challenging, and face presentation may be misdiagnosed as frank breech. To avoid any confusion, a bedside ultrasound scan can be performed. [6]  Ultrasound imaging can show a reduced angle between the occiput and the spine or the chin is separated from the chest. However, ultrasound does not provide much predictive value for the outcome of labor. [7]

• Anatomy and Physiology

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

Planes and Diameters of the Pelvis

The 3 most important planes in the female pelvis are the pelvic inlet, mid-pelvis, and pelvic outlet. Four diameters can describe the pelvic inlet: anteroposterior, transverse, and 2 obliques. Furthermore, based on the landmarks on the pelvic inlet, there are 3 different anteroposterior diameters named conjugates: true conjugate, obstetrical conjugate, and diagonal conjugate. Only the latter can be measured directly during the obstetric examination. The shortest of these 3 diameters is obstetrical conjugate, which measures approximately 10.5 cm and is the distance between the sacral promontory and 1 cm below the upper border of the symphysis pubis. This measurement is clinically significant as the fetal head must pass through this diameter during the engagement phase. The transverse diameter measures about 13.5 cm and is the widest distance between the innominate line on both sides. The shortest distance in the mid pelvis is the interspinous diameter and usually is only about 10 cm. 

Fetal Skull Diameters

There are 6 distinguished longitudinal fetal skull diameters:

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

Cardinal Movements of Normal Labor

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

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

• Indications

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

• Contraindications

Vaginal delivery of face presentation is contraindicated if the mentum is lying posteriorly or is in a transverse position. In such a scenario, the fetal brow is pressing against the maternal symphysis pubis, and the short fetal neck, which is already maximally extended, cannot span the surface of the maternal sacrum. In this position, the diameter of the head is larger than the maternal pelvis, and it cannot descend through the birth canal. Therefore, the cesarean section is recommended as the safest mode of delivery for mentum posterior face presentations. Attempts to manually convert face presentation to vertex, manual or forceps rotation of the persistent posterior chin to anterior are contraindicated as they can be dangerous. Persistent brow presentation itself is a contraindication for vaginal delivery unless the fetus is significantly small or the maternal pelvis is large.

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

Consultations that are typically requested for patients with delivery of face/brow presentation include the following:

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

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

• Technique or Treatment

Mechanism of Labor in Face Presentation

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

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

Mechanism of Labor in Brow Presentation

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

• Complications

As the cesarean section is becoming a more accessible mode of delivery in malpresentations, the incidence of maternal and fetal morbidity and mortality during face presentation has dropped significantly. [10]  However, some complications are still associated with the nature of labor in face presentation. Due to the fetal head position, it is more challenging for the head to engage in the birth canal and descend, resulting in prolonged labor. Prolonged labor itself can provoke fetal distress and arrhythmias. If the labor arrests or signs of fetal distress appear on CTG, the recommended next step in management is an emergency cesarean section, which in itself carries a myriad of operative and post-operative complications. Finally, due to the nature of the fetal position and prolonged duration of labor in face presentation, neonates develop significant edema of the skull and face. Swelling of the fetal airway may also be present, resulting in respiratory distress after birth and possible intubation.

• Clinical Significance

During vertex presentation, the fetal head flexes, bringing the chin to the chest, forming the smallest possible fetal head diameter, measuring approximately 9.5 cm. With face and brow presentation, the neck hyperextends, resulting in greater cephalic diameters. As a result, the fetal head engages later, and labor progresses more slowly. Failure to progress in labor is also more common in both presentations compared to the vertex presentation. Furthermore, when the fetal chin is in a posterior position, this prevents further flexion of the fetal neck, as browns are pressing on the symphysis pubis. As a result, descending through the birth canal is impossible. Such presentation is considered undeliverable vaginally and requires an emergency cesarean section. Manual attempts to change face presentation to vertex or manual or forceps rotation to mentum anterior are considered dangerous and discouraged.

• Enhancing Healthcare Team Outcomes

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

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

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

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

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

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Abnormal Fetal lie, Malpresentation and Malposition

Original Author(s): Anna Mcclune Last updated: 1st December 2018 Revisions: 12

• 1 Definitions
• 2 Risk Factors
• 3.2 Presentation
• 3.3 Position
• 4 Investigations
• 5.1 Abnormal Fetal Lie
• 5.2 Malpresentation
• 5.3 Malposition

The lie, presentation and position of a fetus are important during labour and delivery.

In this article, we will look at the risk factors, examination and management of abnormal fetal lie, malpresentation and malposition.

Definitions

• Longitudinal, transverse or oblique
• Cephalic vertex presentation is the most common and is considered the safest
• Other presentations include breech, shoulder, face and brow
• Usually the fetal head engages in the occipito-anterior position (the fetal occiput facing anteriorly) – this is ideal for birth
• Other positions include occipito-posterior and occipito-transverse.

Note: Breech presentation is the most common malpresentation, and is covered in detail here .

Fig 1 – The two most common fetal presentations: cephalic and breech.

Risk Factors

The risk factors for abnormal fetal lie, malpresentation and malposition include:

• Multiple pregnancy
• Uterine abnormalities (e.g fibroids, partial septate uterus)
• Fetal abnormalities
• Placenta praevia
• Primiparity

Identifying Fetal Lie, Presentation and Position

The fetal lie and presentation can usually be identified via abdominal examination. The fetal position is ascertained by vaginal examination.

For more information on the obstetric examination, see here .

• Face the patient’s head
• Place your hands on either side of the uterus and gently apply pressure; one side will feel fuller and firmer – this is the back, and fetal limbs may feel ‘knobbly’ on the opposite side

Presentation

• Palpate the lower uterus (above the symphysis pubis) with the fingers of both hands; the head feels hard and round (cephalic) and the bottom feels soft and triangular (breech)
• You may be able to gently push the fetal head from side to side

The fetal lie and presentation may not be possible to identify if the mother has a high BMI, if she has not emptied her bladder, if the fetus is small or if there is polyhydramnios .

During labour, vaginal examination is used to assess the position of the fetal head (in a cephalic vertex presentation). The landmarks of the fetal head, including the anterior and posterior fontanelles, indicate the position.

Fig 2 – Assessing fetal lie and presentation.

Investigations

Any suspected abnormal fetal lie or malpresentation should be confirmed by an ultrasound scan . This could also demonstrate predisposing uterine or fetal abnormalities.

Abnormal Fetal Lie

If the fetal lie is abnormal, an external cephalic version (ECV) can be attempted – ideally between 36 and 38 weeks gestation.

ECV is the manipulation of the fetus to a cephalic presentation through the maternal abdomen.

It has an approximate success rate of 50% in primiparous women and 60% in multiparous women. Only 8% of breech presentations will spontaneously revert to cephalic in primiparous women over 36 weeks gestation.

Complications of ECV are rare but include fetal distress , premature rupture of membranes, antepartum haemorrhage (APH) and placental abruption. The risk of an emergency caesarean section (C-section) within 24 hours is around 1 in 200.

ECV is contraindicated in women with a recent APH, ruptured membranes, uterine abnormalities or a previous C-section .

Fig 3 – External cephalic version.

Malpresentation

The management of malpresentation is dependent on the presentation.

• Breech – attempt ECV before labour, vaginal breech delivery or C-section
• Brow – a C-section is necessary
• If the chin is anterior (mento-anterior) a normal labour is possible; however, it is likely to be prolonged and there is an increased risk of a C-section being required
• If the chin is posterior (mento-posterior) then a C-section is necessary
• Shoulder – a C-section is necessary

Malposition

90% of malpositions spontaneously rotate to occipito-anterior as labour progresses. If the fetal head does not rotate, rotation and operative vaginal delivery can be attempted. Alternatively a C-section can be performed.

• Usually the fetal head engages in the occipito-anterior position (the fetal occiput facing anteriorly) - this is ideal for birth

If the fetal lie is abnormal, an external cephalic version (ECV) can be attempted - ideally between 36 and 38 weeks gestation.

• Breech - attempt ECV before labour, vaginal breech delivery or C-section

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

• Variations in Fetal Position and Presentation |

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

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

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

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

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

Head first (called vertex or cephalic presentation)

Facing backward (occiput anterior position)

Spine parallel to mother's spine (longitudinal lie)

Neck bent forward with chin tucked

Arms folded across the chest

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

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

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

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

The fetus has a birth defect .

There is more than one fetus (multiple gestation).

Position and Presentation of the Fetus

Variations in Fetal Position and Presentation

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

Occiput posterior position

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

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

Breech presentation

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

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

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

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

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

Labor starts too soon (preterm labor).

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

Other presentations

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

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

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

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

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• Volume 14, Issue 9
• RidStress 2 randomised controlled trial protocol: an Australian phase III clinical trial of intrapartum sildenafil citrate or placebo to reduce emergency caesarean birth for fetal distress in women with small or suboptimally grown infants at term (≥37 we…
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• Tegan Triggs 1 , 2 , 3 ,
• Nadia Badawi 4 , 5 ,
• Kylie Crawford 1 ,
• http://orcid.org/0000-0002-8249-9516 Helen Liley 1 , 6 ,
• Christoph Lehner 2 , 3 ,
• Rachael Nugent 7 ,
• Karl Kristensen 8 ,
• Fabrício da Silva Costa 8 ,
• William Tarnow-Mordi 9 , 10 ,
• http://orcid.org/0000-0003-0832-4811 Sailesh Kumar 1 , 2 , 3 , 9 , 10
• 1 Mater Research Institute The University of Queensland , South Brisbane , Queensland , Australia
• 2 Women's and Newborn Services , Royal Brisbane and Women's Hospital , Herston , Queensland , Australia
• 3 The University of Queensland Faculty of Medicine , Herston , Queensland , Australia
• 4 Cerebral Palsy Alliance , Forestville , New South Wales , Australia
• 5 The University of Sydney , Sydney , New South Wales , Australia
• 6 Neonatal Critical Care Unit , Mater Mothers' Hospital , Brisbane , Queensland , Australia
• 7 Obstetrics and Gynaecology , Sunshine Coast University Hospital , Sunshine Coast , Queensland , Australia
• 8 Maternal Fetal Medicine Unit , Gold Coast University Hospital , Southport , Queensland , Australia
• 9 NHMRC Clinical Trials Centre , The University of Sydney , Sydney , New South Wales , Australia
• 10 NHMRC Clinical Trials Centre , Camperdown , New South Wales , Australia
• Correspondence to Professor Sailesh Kumar; sailesh.kumar{at}mater.uq.edu.au

Introduction Small for gestational age (SGA) infants are at increased risk of fetal distress in labour requiring emergency operative birth (by caesarean section (CS), vacuum or forceps). We have previously shown that maternal oral sildenafil citrate (SC) in labour halves the need for operative birth for suspected fetal distress in women with appropriately grown term infants.

Methods and analysis RidStress 2 is a phase III randomised, double-blinded, placebo-controlled trial of 660 women with an SGA or suboptimally grown fetus (estimated fetal weight or abdominal circumference<10th centile for gestational age) planning a vaginal birth at term. The trial will determine whether oral intrapartum SC (50 mg eight hourly) reduces the relative risk of emergency CS for fetal distress compared with placebo. The primary outcome is CS for fetal distress, and the secondary outcomes are any operative birth for fetal distress, cost-effectiveness of SC treatment and 2-year childhood neurodevelopmental outcomes. To detect a 33% reduction in the primary outcome from 30% to 20% for an alpha of 0.05 and power of 80% with 10% dropout, requires approximately 660 women (330 in each arm). This sample size will also yield >90% power to detect a similar reduction for the secondary outcome of any operative birth (CS or instrumental vaginal birth) for fetal distress.

Ethics and dissemination Ethics approval was granted by the Mater Misericordiae Limited Human Research Ethics Committee (EC00332) on 11 September 2020. We plan to disseminate the results of this randomised controlled trial through presentations at scientific meetings and peer-reviewed journals, adhering to all relevant reporting guidelines.

Trial registration number RidStress 2 is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12621000354886, 29/03/2021) and the Therapeutic Goods Association of Australia (date registered: 16 March 2021).

• Fetal medicine
• Neonatology
• Clinical Trial
• Perinatology
• Primary Prevention

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:  http://creativecommons.org/licenses/by-nc/4.0/ .

https://doi.org/10.1136/bmjopen-2023-082945

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STRENGTHS AND LIMITATIONS OF THIS STUDY

RidStress 2 will prospectively determine if intrapartum maternal oral sildenafil citrate reduces the risk of emergency operative birth for fetal distress in small for gestational age infants.

By assessing neurodevelopmental outcomes at 2 years of age in offspring, longer-term benefits or harm can be ascertained.

For efficient recruitment, RidStress 2 recruitment will be limited to larger tertiary centres in Queensland. This may limit generalisability beyond the tertiary setting.

Background and rationale

Small for gestational age (SGA) infants (birthweight<10th centile for gestational age) and those with fetal growth restriction (FGR) are at greater risk of developing fetal distress in labour and requiring operative birth, 1–3 compared with their appropriately grown counterparts. Due to underlying placental dysfunction (which limits nutrient and oxygen transfer), 4 5 this cohort poorly tolerates the intermittent hypoxic episodes generated by uterine contractions during labour. 6 They are thus unable to substantially use anaerobic metabolism to generate energy because of reduced cardiac and hepatic glycogen stores. 7–10 10 The hypoxic challenge of labour rapidly diminishes these stores, leading to impaired myocardial function, 11 cerebral hypoperfusion 12 and consequent fetal distress 13 and acidosis, 12 necessitating emergency caesarean section (CS) or instrumental vaginal birth (IVB). 2 14 15

Intrapartum fetal distress is the primary indication for ~23% of CS births in Australia. 16 Both emergency CS and IVB are associated with significant maternal and neonatal morbidity 17–19 as well as implications for future pregnancies. 20–22 Effective strategies to reduce emergency CS and IVB rates related to intrapartum fetal distress are thus urgently needed and are important research priorities. 18 23

Sildenafil citrate (SC) is a phosphodiesterase-5 inhibitor (PDE-5) and potent vasodilator, which prevents intracellular degradation of cyclic guanosine monophosphate and increases bioavailability of nitric oxide. 24 25 PDE-5 is present in smooth muscle of blood vessels, including those of the uterus and placenta. 24 26 SC has been shown to improve fetoplacental blood flow in pregnancies complicated by FGR 27–29 and has a favourable safety profile in pregnancy. 30 31

Our earlier phase II randomised controlled trial (RCT) (RidStress) 30 demonstrated that compared with placebo, intrapartum oral SC reduced emergency operative birth for fetal distress by 51% (RR 0.49, 95% CI 0.33 to 0.73, p=0.0004) and halved rates of pathological fetal heart rate patterns (15% vs 32%; RR 0.48, 95% CI 0.31 to 0.75, p=0.0009) for women in term labour. A subgroup analysis of women with infants weighing <10th centile for the study cohort demonstrated a non-significant reduction in operative birth (CS and IVB) for fetal distress (11.8% vs 38.5%; RR 0.31, 95% CI 0.07 to 1.33) and double the spontaneous vaginal birth rate (82.4% vs 38.5%; RR 2.14, 95% CI 1.04 to 4.41, p=0.02). We also demonstrated that women in the SC arm had a lower intrapartum decline in placental growth factor (PlGF) levels in labour, and the possible protective effect of SC was greatest in those with pretreatment PlGF levels of 85–400 pg/mL (p=0.004). 32 PlGF is a marker of placental function and has an important role in promoting angiogenesis and endothelial cell proliferation. 33 34

The aim of this phase III RCT is to investigate if, compared with placebo, SC safely reduces emergency operative birth for fetal distress in women with SGA or suboptimally grown infants planning a vaginal birth at term. RidStress 2 will also contribute to an individual participant data prospective meta-analysis with considerably greater power to detect moderate benefits and harms.

Safely reducing CS births is an international research priority, 20 23 particularly in low-income and middle-income countries (LMICs), which might experience even greater obstetric and perinatal benefits. Although LMICs have very high rates of SGA infants, 35 they often lack the facilities for intrapartum monitoring and emergency operative birth, resulting in avoidable intrapartum stillbirths or neonatal deaths after birth asphyxia. The vast majority of all stillbirths occur in LMIC, with half occurring in labour. 17 35 SC is now off-patent, inexpensive, stable, easily administered orally with a favourable safety profile in about 1000 women so far. 31 If routine intrapartum SC safely reduces adverse birth outcomes and/or emergency operative birth and their long-term sequelae, it could improve maternal and neonatal outcomes of clinical care across a diverse range of healthcare settings and provide an important option for women attempting vaginal birth worldwide.

We hypothesised that women with an SGA infant may derive greater benefit from intrapartum SC therapy, resulting in lower rates of intrapartum fetal compromise and emergency operative birth for fetal distress.

Aims and objectives

This study aims to test the hypotheses that up to three oral doses of 50 mg SC (vs placebo) is safe and will reduce the relative risk of emergency operative birth for fetal distress in women with an SGA or suboptimally grown fetus.

Our objective is to undertake a 4-year, phase III RCT (RidStress 2) of 660 women with suspected SGA or FGR planning a vaginal birth at term ( population ), to test if SC ( intervention ) safely reduces the relative risk of emergency CS for fetal distress by 33% (from 30% to 20%) ( primary outcome ) compared with placebo ( comparator ). An assessment of infant neurodevelopmental outcomes at 2 years will be undertaken, and a health economic analysis will be conducted.

Primary objective

To evaluate whether, compared with placebo, SC achieves a 33% reduction (from 30% to 20%) in the relative risk of emergency CS for fetal distress (primary outcome).

Secondary objectives

To evaluate whether, compared with placebo, SC reduces the relative risk of any operative birth (CS and IVB) for fetal distress by 33% (from 40% to 26%) and has similar perinatal and maternal outcomes.

To evaluate whether, compared with placebo, SC reduces rates of neurodevelopmental delay at 2 years of age.

To evaluate whether, compared with placebo, SC is cost-effective.

To evaluate whether prelabour maternal PlGF or soluble Fms-like tyrosine kinase-1 (sFlt-1), fetal biometry or fetoplacental Doppler assessment can stratify women who would benefit more from intrapartum SC therapy.

Methods and analysis

Trial design.

RidStress 2 is a two-arm parallel, randomised (1:1), placebo-controlled, double-blind, multicentre, superiority trial of intrapartum SC versus placebo in 660 women with a suspected SGA or suboptimally grown fetus at term (≥37 +0 weeks’ gestation).

Trial setting

RidStress 2 will be conducted at the Mater Mothers’ Hospital, Royal Brisbane and Women’s Hospital, Sunshine Coast University Hospital and Gold Coast University Hospital in Queensland, Australia. Recruitment to RidStress 2 began on 27 July 2021, and recruitment is planned to continue until 11 September 2025.

Patient and public involvement statement

We involved clinician and consumer groups when designing this trial.

Study population

Inclusion criteria:

Singleton pregnancy.

Planning a vaginal birth at term (>37 weeks’ gestation).

Aged>18 years and able to give informed consent.

Pregnancy complicated by suspected SGA infant or late FGR.

SGA is defined as estimated fetal weight (EFW) or abdominal circumference (AC) <10th centile for gestation based on ultrasound assessment.

FGR 36 is defined as EFW or AC <3rd centile or two out of three of the following:

EFW or AC <10 th centile.

AC or EFW crossing centiles by >2 quartiles on growth charts (for the purposes of this trial, we defined this change over a minimum interval of 4 weeks).

Cerebroplacental ratio< 5th centile or Umbilical Artery Pulsatility Index> 95th centile for gestation.

Exclusion criteria:

Two or more previous CS births.

Previous classical CS.

Major fetal anomaly in this pregnancy.

Non-cephalic presentation.

Severe hepatic or renal impairment.

Participants who are taking any type of nitrate drug therapy or who use short-acting nitrate-containing medications during labour (such as sodium nitroprusside, bosentan, fosamprenavir and ritonavir combination, hepatic enzyme inhibitors CYP3A4 (including itraconazole, ketoconazole, ritonavir, cimetidine, erythromycin, saquinavir, darunavir), or hepatic enzyme substrates (CYP3A4), medications used to treat pulmonary arterial hypertension, and other phosphodiesterase type 5 inhibitors like riociguat), due to the risk of potentially life-threatening hypotension.

Screening, registration and randomisation

This is summarised in figure 1 . Women will be screened for eligibility and approached by obstetric caregivers or research midwives to participate in the trial from 32 weeks’ gestation onwards. A confidential record of women who were screened for eligibility, approached and consented will be kept at each study site. For women who decline participation, a reason will be recorded where given. The rights of women to decline participation without providing a reason will be respected.

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Schedule of enrolment, interventions and assessments for RidStress 2.

Signed consent to enter the study will only be obtained by members of the study team after full explanation and adequate time for consideration of information detailed in the patient information and consent form ( online supplemental appendix 1 ). Consent may be obtained in-person, over the phone or by email. All participants will be free to withdraw from the trial at any time without reason or prejudice of their ongoing care. Women will receive no financial incentive to participate in this study. Their participation will be documented in their obstetric record and alerts placed on the relevant electronic patient administration systems. An email will be sent to women following their registration providing contact details for the trial staff and a copy of their signed patient information and consent form. All women will receive routine obstetric care until the onset of spontaneous labour or induction of labour (IOL).

Supplemental material

Women will also be invited to consent to participate in childhood neurodevelopmental follow-up. If they consent, contact details will be recorded and follow-up assessment will be performed as described below. If consent is declined or withdrawn before follow-up takes place (2 years corrected age), no further contact will take place.

Prior to IOL or spontaneous labour, 20 mL of blood will be collected for assay of soluble sFlt-1 and PlGF levels. Excess serum and plasma will be aliquoted and stored for future related research at Mater Research Institute, University of Queensland, for which separate ethical approvals will be obtained. This is outlined in the patient information and consent form.

Interventions

The study intervention is oral SC 50 mg, and the comparator will be an identical matching placebo. The trial medication will be given when participating women are admitted to the labour ward, either in spontaneous labour or for IOL (artificial rupture of membranes ± syntocinon infusion). Women will be given the study treatment by the attending midwife in the labour ward. Women will receive SC 50 mg or identical placebo orally every 8 hours until birth of the baby to a maximum of three doses. Participants who satisfy the below criteria will have their treatment ceased:

Acute severe maternal hypotension (<60/40 mm Hg × three episodes) sufficient to cause maternal and/or fetal compromise occurs.

The participant requests discontinuation from study.

The investigative team believes it is in the best interest of the participant on grounds of safety or side effect or tolerability that discontinuation takes place.

To monitor adherence to the trial intervention, the date and time of study drug administration will be recorded, unused investigational product will be returned to pharmacy, and accountability logs will be kept. An instruction sheet outlining trial processes will be provided to the attending midwife, and 24-hour phone support will be provided by the research team. Both the clinical and research teams will collaborate to monitor adherence to trial processes.

Management of labour and puerperium

Management of labour will be in accordance with local protocols and guidelines. All women will have continuous electronic intrapartum fetal heart rate monitoring, with abnormalities classified according to Royal Australian and New Zealand College of Obstetricians and Gynaecologists guidelines. 15 In the event of operative birth, the attending obstetrician will be asked to confirm the indication for operative birth and the role that fetal distress played in their decision-making.

Umbilical artery cord pH will be measured in all women after birth. Delayed cord clamping will always be facilitated. Where possible, 20 mL of cord blood will be collected for SC assays and storage for future research related to this study. The placenta will be sent for routine histopathological examination as per institutional guidelines. All biospecimens will be registered and stored at the Mater Research Institute in Brisbane, Australia.

All infants will also receive routine oxygen saturation screening 24–48 hours after birth (current standard practice in Australia). This test complements the newborn physical examination and is used to detect hypoxaemia in infants. Infants with oxygen saturation>95% are very unlikely to have major congenital heart or significant pulmonary disease (including persistent pulmonary hypertension of the newborn). Infants with oxygen saturations<95% will receive further assessment by the paediatric team and additional investigations will be performed as required.

Trial outcomes

Primary outcome.

Emergency CS for fetal distress (defined contemporaneously as an abnormality in fetal heart rate pattern, fetal scalp lactate or pH).

Secondary outcomes

Any operative birth (CS or IVB) for fetal distress, health economic costs, 2-year childhood neurodevelopmental outcomes and correlation between maternal placental biomarkers, prelabour ultrasound variables.

Obstetric and maternal outcomes

Other indications for operative birth, spontaneous vaginal birth, postpartum haemorrhage (blood loss>1.5 L), blood transfusion, peripartum hysterectomy, uterine rupture, third and fourth degree tears, length of stay in hospital, intensive care unit admission.

Perinatal outcomes

Intrapartum stillbirth or neonatal death<28 days, Apgar≤4 at 5 min, severe acidosis (cord artery pH<7.0 or base excess < −12 mmol/L), neonatal encephalopathy, seizures, respiratory support>4 hour, neonatal intensive care unit (NICU) admission>48 hours, persistent pulmonary hypertension of the newborn or meconium aspiration syndrome.

Sample size

The incidence of the primary outcome is estimated at 30% based on data in a large recent RCT in term pregnancies 37 and local data from Mater Mother’s Hospital. To detect a 33% reduction in the primary outcome from 30% to 20% for an alpha of 0.05 and 80% power with 10% dropout in each arm needs approximately 660 women (330 in each arm) ( https://www.stat.ubc.ca/%7Erollin/stats/ssize/b2.html ). This sample size will also yield>90% power to detect a similar reduction for the secondary outcome of any operative birth (CS or IVB) for fetal distress.

Allocation and concealment of intervention

A computer-generated randomisation schedule with permuted block randomisation with randomly selected block sizes will be used. The block sizes and the randomisation schedule will be concealed to clinical staff, research staff and participants. Stratification will be performed by study site to ensure balance in treatment assignment across sites. The randomisation schedule was provided to the pharmaceutical manufacturer and identical trial medication kits containing either SC 50 mg or placebo were produced and numbered sequentially. Kits were then allocated sequentially to registered participants by the research staff.

Participants, research staff and healthcare providers will remain blinded to intervention allocation. Assessments of all outcomes and data analysis will be performed in a blinded manner. If emergency unblinding is deemed in the best interest of the participant or their infant, authority to do so will be obtained from the principal investigator, trial statistician and pharmacist. Unblinding will only occur if knowledge of the allocated treatment group is essential for ongoing management of the patient or their infant. The need for unblinding should be very uncommon, as the study intervention is rarely associated with severe side effects. 31

Data collection and management

All data collection will be recorded into electronic case report forms and stored in a secure online database (RedCap). Valid values, expected ranges and descriptions selected from a list will be specified in the electronic database to ensure data integrity. Baseline demographic and obstetric data will be entered into the RedCap database at the time of registration. Data for primary and secondary outcomes will be ascertained by reviewing the participants’ medical records and cross-checked against details provided by the treating obstetrician. Adverse maternal and neonatal outcomes will be assessed by review of the participants’ medical records at 7 days and at the 28-day follow-up. When the infant approaches 2 years, participants will be sent an electronic version of the Ages and Stages Questionnaire. 38 To promote retention of trial participants until the time of neurodevelopmental follow-up, 6 monthly phone calls to participants will be made.

Data analysis plan

Primary and secondary outcome analyses will adhere to an intention-to-treat basis, so all women randomised are analysed in their allocated group, using generalised linear models (binary or normal). Intervention effect will be presented as relative risk or mean difference as appropriate, with 95% CIs. Two-tailed p value<0.05 will be considered statistically significant. Primary analyses will be unadjusted. Number needed to screen and treat to prevent one adverse primary outcome will be calculated. Where there are differences in the baseline characteristics between the two treatment groups that might be associated with outcomes, secondary adjusted analysis of the primary outcome will be carried out using multiple (log-binomial) regression. No adjustment will be made for multiple comparisons. Reporting of findings will be done in accordance with Consolidated Standards of Reporting Trials 39 and Transparent Reporting of a multivariable prediction model for Individual Prognosis or Diagnosis 36 guidelines.

Oversight and monitoring

Trial management committee (tmc).

The TMC consists of all chief investigators for each participating site, and the coordinating centre is located at the Mater Mothers’ Hospital and Mater Research—University of Queensland. Participating sites include the Mater Mother’s Hospital, Royal Brisbane and Women’s Hospital, Sunshine Coast University Hospital and Gold Coast University Hospital. The TMC will oversee and plan the conduct of the study at each site including aspects of monitoring, recruitment, progress, data management, modifications to the study protocol, adverse event reporting, Human Research Ethics Committee (HREC) and local governance approvals, consideration of relevant information from new research, and implementation of recommendations from external bodies and reviewing committees, including the Independent Data and Safety Monitoring Committee (IDSMC). Such recommendations may include modification of the study protocol, or stopping of the trial based on interim analysis, or other relevant information or advice. The TMC will be responsible for communicating any changes to the protocol or study conduct to participating sites, investigators, registries, journals or regulators.

Independent Data and Safety Monitoring Committee (IDSMC)

A joint IDSMC who will oversee both RidStress 2 and iSEARCH (published in this BMJ Open issue and linked to this manuscript) has been established. The IDSMC will meet at least annually and comprises three perinatal care clinicians/researchers (one serving as Chair) and a biostatistician. All IDSMC members will be independent of sponsor, trial conduct and membership will be restricted to those that are free of significant conflicts of interest. The role of the IDSMC is to safeguard the interests of study participants by reviewing interim data on the primary outcome, adverse events and other outcome data after 50% recruitment or as appropriate (as per Peto et al , Haybittle, and Geller and Pocock). 37 40 41 There will be no adjustment to alpha for interim analyses. The IDSMC will provide the TMC a report outlining their recommendations.

Interim analyses of the primary composite outcome

The IDSMC will advise the TMC if they consider there is proof beyond reasonable doubt of net benefit or harm for the primary outcome, employing a commonly used formal threshold of p<0.001 for nominal significance, as recommended by Geller and Pocock. 41

Interim analyses of mortality

The IDSMC will advise the TMC if they support the view that there is a difference in mortality due to intrapartum stillbirth and/or 28-day neonatal mortality identified as a deviation from the null indicated by a Haybittle-Peto boundary of 3 standard errors from the null, which is equivalent to p<0.0027, 37 40 which would be needed to justify recommending early stopping.

Safety and adverse event reporting

We will adhere to National Health and Medical Research Council guidelines for safety monitoring and serious adverse event (SAE) reporting in clinical trials involving therapeutic goods. 42–44 All SAEs occurring from the time of administration of the trial medication until hospital discharge will be reported to the sponsor with oversight provided by the IDSMC. Adverse events will be assessed for causality, as ‘expected’ or ‘unexpected’ with consideration given to the temporal relationship between administration of the trial medication and SAE. Possible adverse drug reactions (summarised in online supplemental appendix 2 ) 45 will be recorded.

In addition, the following maternal and neonatal events will also be reported as SAEs for this study:

Maternal SAEs:

Maternal intensive care unit admission.

Maternal hypotension (<60/40 mm Hg × three episodes) requiring medical intervention.

Major postpartum haemorrhage>1500 mL.

Persistent visual changes requiring ophthalmic review.

Maternal death prior to discharge from hospital.

Neonatal SAEs:

Admission to NICU for >48 hours.

Cord arterial pH<7.0.

Hypoxic ischaemic encephalopathy.

Neonatal seizure.

Intrapartum stillbirth.

Neonatal death prior to discharge from hospital.

Compliance and auditing

The trial will be conducted in compliance with full good clinical practice recommendations 46 and will be subject to annual inspection and audit by Mater Misericordiae Limited under their remit as sponsor. The study will comply with all applicable laws and regulations and the principles laid down by the World Medical Association in the Declaration of Helsinki 2013. It is registered with the Australian and New Zealand Clinical Trial Registry. Trial results will be disseminated as soon as practical via presentations at clinical, academic and scientific meetings, peer-reviewed journals and general media. We will adhere to all relevant reporting guidelines.

Ethics and dissemination

Ethics approval was granted by the Mater Misericordiae Limited Human Research Ethics Committee (EC00332) on 11 September 2020. We plan to disseminate the results of this RCT through presentations at scientific meetings and peer-reviewed journals, adhering to all relevant reporting guidelines.

Ethics statements

Patient consent for publication.

Not applicable.

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X @williamotm

TT and SK contributed equally.

Contributors SK conceived the study and is the guarantor. All authors (TT, SK, HL, CL, RN, KK, NB, FdSC, KC and WTM) made substantial contributions to the study design. KC provided advice and guidance for the proposed statistical analysis. TT and SK contributed equally to the manuscript. All authors reviewed and approved the final version before submission and agreed to be accountable for all aspects of the work.

Funding This work is funded by The Royal Brisbane and Women’s Hospital Foundation (RBWH-EOI-2021-078), Royal Australian College of Obstetricians and Gynaecologists Women’s Health Foundation—Norman Beischer Clinical Research Scholarship (2021–2022), Research Foundation of the Cerebral Palsy Alliance—PhD Project Grant (PHD00120) and Sunshine Coast Hospital and Health Foundation—Wish List Grant (2020-19).

Competing interests None declared.

Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods and analysis section for further details.

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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