what is anterior presentation in pregnancy

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

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

Fetal presentation and position

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

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

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

Medical illustrations by Jonathan Dimes

Head down, facing down (anterior position)

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

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

Head down, facing up (posterior position)

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

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

Frank breech

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

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

Complete breech

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

Incomplete breech

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

Single footling breech

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

Double footling breech

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

Transverse lie

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

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

Oblique lie

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

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

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

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

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

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

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

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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 (ecv), malpresentation, breech pregnancy, search our site for.

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Breech presentation and turning the baby

In preparation for a safe birth, your health team will need to turn your baby if it is in a bottom first ‘breech’ position.

Read more on WA Health website

Breech Presentation at the End of your Pregnancy

Breech presentation occurs when your baby is lying bottom first or feet first in the uterus (womb) rather than the usual head first position. In early pregnancy, a breech position is very common.

Read more on RANZCOG - Royal Australian and New Zealand College of Obstetricians and Gynaecologists website

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

Read more on NSW Health website

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.

Read more on Pregnancy, Birth & Baby website

Malpresentation is when your baby is in an unusual position as the birth approaches. Sometimes it’s possible to move the baby, but a caesarean maybe safer.

Labour complications

Even if you’re healthy and well prepared for childbirth, there’s always a chance of unexpected problems. Learn more about labour complications.

ECV is a procedure to try to move your baby from a breech position to a head-down position. This is performed by a trained doctor.

Having a baby

The articles in this section relate to having a baby – what to consider before becoming pregnant, pregnancy and birth, and after your baby is born.

Anatomy of pregnancy and birth - pelvis

Your pelvis helps to carry your growing baby and is tailored for vaginal births. Learn more about the structure and function of the female pelvis.

Planned or elective caesarean

There are important things to consider if you are having a planned or elective caesarean such as what happens during and after the procedure.

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Baby positions in the womb before birth

Read time 5 minutes

You might be wondering how your baby is lying in your womb and how that might affect labour. Here's what you need to know about baby positions...

What is the best position for my baby to be in?

"The best position for your baby to be in ready for their birth, is head down, facing your back, with their back against your belly."

In this position, your baby’s head and neck are flexed and their chin is tucked into their chest. This means the narrowest part of their head (the back) presses on your cervix, helping it to open.

The flexible joints in your baby’s skull allow your baby’s head to change shape and make its way more easily down the birth canal during labour . This helps them fit through your pelvis more easily (Simpkin, 2010; RCM, 2012) .

What is the ‘occiput anterior’ position?

If your baby is lying head down in your womb and facing your back, like described above, they’re in what medics call the occiput anterior (OA) position. This means that the back of their head (occiput) is at the front (anterior). Most babies lay this way and it’s the best position for birth (RCM, 2012) .

Which other positions might my baby be lying in?

• If your baby is lying in your womb to your left, you’ll see LOA (left occiput anterior) written in your maternity notes .
• If they are lying in your womb to your right, you’ll see ROA (right occiput anterior) written in your notes.
• If your baby is bottom down in your womb, you’ll see B or BR (breech) written in your notes – see our article on breech babies . 
• Back-to-back – see below.
• See our article about maternity notes to find out the other abbreviations for baby positions that your midwife might note.

My baby is ‘back-to-back’, what does it mean?

Some babies lie with their back against their mother’s back. This is known as an occiput posterior (OP) position or back-to-back position in the womb.

Labour tends to take longer, be more painful and you’re more likely to have a caesarean or assisted (instrumental) birth if your baby is in a posterior position. This is because they can’t tuck their chin in very easily, which makes getting through the pelvis more awkward. This position often causes backache during labour too (Simpkin, 2010; RCM, 2012; Tommy’s, 2016) .

What can I do to help my baby to turn?

Some people think that women with babies in the back-to-back position can use certain positions during the end of pregnancy to turn their babies. Forward-leaning positions like going on all fours have in the past been said to help babies into the best position for birth . Unfortunately, there is no evidence that this works (Guitier et al, 2016) .

On the plus side, forward-leaning positions could ease your backache when you’re in the first stage of labour (Hunter, 2007; Guitier et al, 2016) .

What position in the womb is my baby in? How to tell whether they’re front or back facing

Your midwife should be able to tell you during an ultrasound which way round your baby is lying. Saying that, babies will move position during pregnancy and birth. So it’s good to know there are some giveaways to how your baby’s lying.

Here are the tell-tale signs you can look out for:

• You might be able to visualise how your baby is lying from their movements. Tickles might be their little hands waving around, while harder movements could be their elbows, knees or feet.
• Your baby’s bum will feel squashier than their head, which will be firm and round.
• If your baby is lying back-to-back (OP position), your bump might feel squashy and you may feel (and see) kicks in the middle of your belly. Another sign of the OP position is a dip around your belly button instead of it poking out.
• If your baby is head down and facing your back (OA position), you’ll probably feel kicks under your ribs. You’ll also be able to feel the hard, rounded surface of your baby’s back, which will be on one side of your belly.

(Tommy’s, 2016)

My baby is not in the ideal position for labour, should I worry?

No, as there isn’t much chance it will be a problem. Most babies turn during labour to the anterior position. Here are the stats:

• Between 15% to 32% of women have a baby in an OP (back-to-back) or occipito-lateral position when they go into labour. This happens more often among women who haven’t given birth before (Simkin, 2010) .
• Only five to eight babies out of every 100 will stay in the OP position (Tommy’s, 2016) .

Taking an antenatal course  could help to prepare you for labour and birth. It could also help to ease any worries you might have about labour and give you the chance to meet other parents in your local area.

This page was last reviewed in July 2018.

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.

We also offer antenatal courses  which are a great way to find out more about pregnancy, labour and life with a new child.

Guittier MJ, Othenin-Girard V, de Gasquet B, Irion O, Boulvain M. (2016) Maternal positioning to correct occiput posterior fetal position during the first stage of labour: a randomised controlled trial. BJOG. 123(13):2199-2207. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5132127/ [Accessed 1st July 2018].

Hunter S, Hofmeyr GJ, Kulier R. (2007) Hands and knees posture in late pregnancy or labour for fetal malposition (lateral or posterior). Cochrane Database Syst Rev. (4):CD001063. Available at: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD001063.pub3/full [Accessed 1st July 2018].

RCM (Royal College of Midwives). (2012) Persistent lateral and posterior fetal positions at the onset of labour. Evidence based guidelines for midwifery-led care in labour. Available at: https://www.rcm.org.uk/sites/default/files/Persistent%20Lateral%20and%20Posterior%20Fetal%20Positions%20%20at%20the%20Onset%20of%20Labour.pdf [Accessed 1st July 2018].

Simkin P. (2010)  The fetal occiput posterior position: state of the science and a new perspective. Birth. 37(1):61-71. Available at: https://www.ncbi.nlm.nih.gov/pubmed/20402724 [Accessed 1st July 2018].

Tommy’s (2016) Getting your baby into the best birth position. Available at: https://www.tommys.org/pregnancy/labour-birth/baby-best-position-birth [Accessed 9th September 2018].

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Delivery presentations

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

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

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

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

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

Occiput Posterior (OP)

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

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

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

Transverse Position

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

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

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

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

Less Common Presentations

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

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

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

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

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

Alternative Names

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

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

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

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

Review Date 11/21/2022

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

Related MedlinePlus Health Topics

What to Know When Your Baby is in the Occiput Anterior Position

In this birthing position, your baby's head is toward your cervix. Their face is toward your back and their back is toward your belly.

During pregnancy, your baby may move into different positions. Your baby usually moves into the birthing position sometime between weeks 32 and 36 of pregnancy.

Are There Benefits of the Occiput Anterior Position?

The occiput anterior position is considered to be one of the best fetal positions. It leads to the best birthing outcomes. With this position there are:

• Fewer unplanned cesarean sections (C-sections)
• On average, faster births
• On average, a less painful birthing process

This is because in the occiput anterior position your baby's head is in the optimal position to help your cervix open naturally. Their soft skull bones are also in the best position to change shape and fit more easily through the birth canal in this position.

Are There Variations of the Occiput Anterior Position?

Some babies are in the direct occiput anterior position, which means their nose is facing your tailbone. However, many babies are rotated slightly to one side. In the left occiput anterior position, your baby's head is slightly rotated toward the left. In the right occiput anterior position, it is slightly toward the right. All three of these positions are considered to be best for giving birth vaginally.

What Are Other Baby Positions in the Womb?

While the occiput anterior position is the most common birthing position, some babies do not descend into this position naturally. Other potential positions include:

Transverse. In this position, your baby's head directly faces either the left or right side of your vaginal canal. Many babies start out in this position during early labor, but then turn to the occiput anterior position as your labor goes on for longer. If they do not turn, your doctor may recommend a tool to help like forceps or a vacuum . In some cases, you might need a cesarean section.

The names for this position are left occiput transverse or right occiput transverse, depending on which direction your baby is facing.

Occiput posterior. This is when your baby's back is facing your back, and their face is toward your belly button. You can have a successful vaginal delivery in this position if you have a large pelvis. However, many babies will need to be helped along with forceps. Depending on the situation, your doctor may keep the baby in this position, or use the forceps to turn the baby into the occiput anterior position as it enters your vaginal canal. Because of this, many pregnant people have faster and less painful births with occiput anterior vs. posterior.

Your baby can be in direct occiput posterior, which is when they are directly facing your belly button. They can also be in right occiput posterior or left occiput posterior if their head is slightly rotated toward one side or the other.

Breech. If your baby is in a breech position, that means their bottom is down toward your cervix and their head is up toward your head. 

Depending on how your baby is rotated, there are several more specific names for breech positions. These include:

• Sacrum anterior. Your baby's head is directly facing your back and their back is facing your belly.
• Left sacrum anterior and right sacrum anterior. The same as sacrum anterior, but slightly rotated to the left or right.
• Right sacrum transverse and left sacrum transverse. Your baby is directly facing the left or right.
• Sacrum posterior. Your baby is back to back with you.
• Left sacrum posterior and right sacrum posterior. The same as sacrum posterior, but slightly turned toward the left or right.

There are also different types of breech positions:

• Frank breech. In this position, your baby's rear end is the first thing that will come out. Their legs are bent up toward their abdomen and their feet are in front of their face.
• Complete breech. In this position, your baby's legs are bent at the knee so their feet are touching their rear end.
• Footling breech. In this position, one or both of your baby's feet will be the first to come out of the birth canal.

All breech positions come with a greater risk of injury during birth. One of the main risks is that the umbilical cord can form a loop around the baby's neck. With breech babies, there is room for the umbilical cord to enter the birth canal before the baby. It can then get folded, cutting off blood supply to the baby before it is born. Finally, because the head is the largest part of the body, it can get stuck during a vaginal birth.

If your baby is in a breech position, your doctor may recommend a cesarean section.

Can You Get Your Baby to Turn?

Many parents wonder if it's possible to encourage their baby to turn because they want to have an occiput anterior delivery. There are things you can try, but none of them are guaranteed to work. You can try spending some time on your hands and knees to encourage your baby to turn their face frontwards. Music, lights, and stimulation may attract your baby to turn toward them. There is also a medical procedure called an external cephalic version that may help your baby to turn from a breech position. However, even if your baby does turn temporarily, they may go back to their original position.

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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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• Left Occiput Anterior

Left Occiput Anterior (LOA)

The Left Occiput Anterior position has the reputation as the best fetal position. Actually, LOA is just one of the best positions to help the baby be in the smallest diameter to fit the pelvis. The LOA baby has his or her back on the mother’s left side. The baby faces towards the mother’s back between the right hip and the spine of his or her mother.

The crown of the LOA baby’s head most often enters the pelvis first. Tucking the chin helps the baby fit the pelvis in a way that the baby’s head can mold (shape) most effectively to fit the pelvis.

The baby’s back can curve most effectively in this position. The baby slides down the softening abdomen in the last weeks of pregnancy to enter the brim. The head enters the pelvic brim at about 38 weeks in a first-time mom, perhaps later in an experienced birthing woman.

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• 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
• OP Truths & Myths
• Anterior Placenta
• Body Balancing

The midwife palpates the fetal head and listens to the baby’s heartbeat with a fetascope (stethoscope). The mother feels a bulge for the baby’s bottom on her left. The feet stretch and kick in her upper right. The midwife may feel the “cephalic promontory” on the right signifying that the baby’s chin is nicely tucked (flexed).

The OA (Occiput Anterior) and LOT (Left Occiput Transverse) fetal positions are also ideal.

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Anterior Placenta

What is an anterior placenta, how can an anterior placenta affect your pregnancy, read this next.

However, if you experience vaginal bleeding, severe abdominal or back pain, or rapid uterine contractions, call your practitioner, as these symptoms could indicate potential placental problems.

What to Expect When You're Expecting , 5th edition, Heidi Murkoff. WhatToExpect.com, Placenta Previa , May 2021. WhatToExpect.com, Your Baby's Placenta , July 2021. Journal of Clinical Ultrasound , Difference in Migration of Placenta According to the Location and Type of Placenta Previa , December 2007. Mayo Clinic, Placenta Previa , May 2020. National Health Service, What Complications Can Affect the Placenta? September 2021. National Institutes of Health, National Library of Medicine, National Center for Biotechnology Information, Placental Location and Pregnancy Outcomes in Nulliparous Women: A Population-based Cohort Study , August 2019. UpToDate.com, Placenta Previa: Management , June 2021.

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Understanding Right Occiput Anterior – ROA fetal position + FAQs

Medically Reviewed by: Dr. Veena Shinde (M.D, D.G.O,  PG – Assisted Reproductive Technology (ART) from Warick, UK) Mumbai, India

• >> Post Created: January 30, 2022
• >> Last Updated: August 26, 2024

Table of Contents - Right Occiput Anterior Position

Medical terms for a baby’s position when entering the mother’s pelvic region just before labor can be daunting. However, it isn’t as intimidating as it may seem; some basic knowledge on the subject can help you in understanding your pregnancy and labor better.

When we talk about baby positions, anterior and posterior are the basic. In both these positions, the baby’s head could be down, towards the cervix or feet could be down (breech baby).

In medical terms, the back of a baby’s head is called the ‘ occiput .’ In this article we have tried to put forth all you need to know about Right Occiput Anterior position (ROA position), risks associated and some of the most common FAQs mothers  who have been told that they have and ROA position in labor have.

What is Right Occiput Anterior position?

Going by the explanation given above, in the ROA fetal position, the baby enters the mother’s pelvic region from the right (R), in the anterior (A) position (facing the mother’s spine).

It might be easier to understand the exact ROA fetal position using the picture of a woman’s pelvic area.

What is Right Occiput Anterior Presentation?

‘Presentation’ in terms of pregnancy is used to describe the baby’s first body part that enters the mother’s pelvic region just before labor.

So there is a difference between ‘presentation’ and ‘position’; presentation primarily gives an understanding if the baby is head-down or breech, while position is in connection with the mother’s body (left, right, anterior, posterior).

Now in Right occiput anterior/ ROA position , presentation will be the top of the baby’s head (also called vertex) , with the baby’s occiput or back towards the mother’s belly.

Movements and kicks in Right Occiput Anterior position (ROA fetal Position)

In Right Occiput Anterior , as the baby’s back and shoulders are on the mother’s right side, the limbs are obviously on the left side, and therefore, any movements are felt by the mother on the left side of the belly.

Baby’s kicks would obviously be felt on the upper left side of the belly in the ROA position.

What are the variables with ROA fetal position that affect labor?

There are certain factors that can affect labor in the ROA fetal position.

• Baby’s chin being towards or away from its chest
• First-time childbirth
• Balance and tone of the soft tissues involved in childbirth (uterus, ligaments, fascia)
• Pelvic shape and size
• Pelvic alignment
• Placenta position

If in ROA position, for any reason, if the head is not getting positioned right, like instead having chin first, then you need to first understand that by easy methods you can slowly try and move your baby in proper head down position through:

• Regular walks – here natural laws of gravity along with movements help in naturally positioning your baby in the right position – head first just before birth
• You could take help of a pregnancy belt as well – in confidence with your doctor or midwife
• A few jiggly movements of hips, buttocks and thighs also helps in loosening the muscles giving space for your baby to move and change the position.

Left Occiput Anterior (LOA position) Vs. Right occiput anterior (ROA position)

The baby’s position while entering the mother’s pelvic region decides how the labor and delivery of the baby will happen.

An Occiput anterior position ( Left occiput Anterior/ LOA position or ROA position), wherein the baby’s face is towards the mother’s spine and back is toward the mother’s belly is the ideal position for birth.

On the other hand, posterior position ( LOP position or ROP position), where the baby’s back is with the mother’s back, could cause a comparatively more painful labor and  likelihood of a C-section for the baby’s birth goes up.

Continue reading below ↓

Read this next

Vertex Presentation: How does it affect your labor & delivery?

Everything you need to know about Placenta Position & Placenta Health – with FAQs

The Ultimate List of Baby Must Haves

Is right occiput anterior fetal position normal.

The Right Occiput Anterior (ROA) position is one of the common baby positions before labor.

Yes, it is one of the normal positions from the various other baby positions, like various breech positions, oblique positions and so on.

Is ROA position bad as compared to the LOA position?

No, ROA is as good as LOA position for the baby before labor.

It is believed that LOA position is better because in most women the left side of the pelvis is slightly larger, giving more space to the baby to grow. However, ROA is also normal and a good baby position.

How to know if the baby is in the anterior position?

If your baby is in the anterior (A) position, it means its back is toward your belly, giving it a characteristic round shape seen in pregnancies.

On the other hand, if the baby is in the posterior (P) position, with its back toward the mother’s back and limbs toward the belly, it will give the belly a bumpier look and a hollow space might be visible around the navel.

How to ensure the baby in the right position during birth?

Having the baby in the best possible position before labor begins or even during labor will not only affect the baby’s delivery, but also ease the labor and birth experience for the mother. With the baby being in the best possible position, it can sometimes cut down the chances of a C-section and make the whole process comparatively less painful.

Your doctor will guide you through the process to get your baby in the best possible position for birth.

Medical professionals say how they have witnessed that when the baby is in the optimal position, both the mother’s and baby’s bodies work together towards delivery in the best way.

Key takeaway

The most important takeaway from this article is that the Right Occiput Anterior / ROA baby position is normal, safe, and one of the optimal baby positions before labor.

Of course, as always, we recommend you to talk to your doctor in case of any doubts or concerns. They will also guide you on how to get your baby to the best possible position for labor and delivery.

Happy Pregnancy!

Khushboo Kirale

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Back to Journals » International Journal of Women's Health » Volume 16

Pregnancy Risk Assessment, Management, and Delivery Plan for Pregnant Women with Moyamoya Disease Using a Multidisciplinary Collaborative Approach: A Case Series

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Authors Li D , Lv F , Ding C   , Zhuang Z , Wang S

Received 26 April 2024

Accepted for publication 24 July 2024

Published 26 August 2024 Volume 2024:16 Pages 1415—1424

DOI https://doi.org/10.2147/IJWH.S472646

Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Dr Marleen van Gelder

Dan Li, 1 Fang Lv, 2 Chenyuan Ding, 3 Zhaohan Zhuang, 3 Shijun Wang 1 1 Department of Obstetrics & Gynecology, Xuanwu Hospital Capital Medical University, Beijing, 100053, People’s Republic of China; 2 Department of Medical Record Statistics, Xuanwu Hospital Capital Medical University, Beijing, 100053, People’s Republic of China; 3 Education Section, Xuanwu Hospital Capital Medical University, Beijing, 100053, People’s Republic of China Correspondence: Shijun Wang, Department of Obstetrics & Gynaecology, Xuanwu Hospital Capital Medical University, No. 45 Changchun Street, Xicheng District, Beijing, 100053, People’s Republic of China, Tel +86-13601222289, Email [email protected] Purpose: This case report aimed to summarize the risk factors, clinical characteristics, imaging changes, and maternal and fetal prognosis associated with Moyamoya disease in pregnant women and to explore effective management strategies and a comprehensive delivery plan. Case Presentation: The clinical data of four pregnant women who were diagnosed with Moyamoya disease and admitted to our hospital between January 2010 and January 2019 were retrospectively analyzed. Their diagnosis, treatment, delivery, and postpartum management during the pregnancy were analyzed. Among the four pregnant women, three were primipara and one was multipara. The age ranged from 27 to 41 years old. The gestational week of termination of pregnancy ranged between 8 and 39 weeks. During pregnancy, one case died in utero; one case was complicated with postpartum hemorrhage; one case was complicated with chronic hypertension, multiple cerebral artery stenosis and occlusion, bilateral middle cerebral artery occlusion, bilateral internal carotid artery occlusion, and Hashimoto’s thyroiditis. Under epidural anesthesia, two cases underwent a lower segment cesarean section; one case underwent artificial abortion; and one case underwent induced labor during late pregnancy. Two newborns survived. Conclusion: Moyamoya disease is a rare and serious complication of pregnancy. Pregnancy and childbirth may exacerbate the progression of this disease or induce cerebrovascular accidents, with a high mortality and disability rate, which seriously threatens the safety of mother and infant lives; however, with the close collaboration of a multidisciplinary team, it is possible to maximize a good pregnancy outcome. Keywords: pregnancy, cerebrovascular lesions, moyamoya disease

Introduction

Moyamoya disease (MMD) is a chronic occlusive cerebrovascular disease characterized by slow thickening of the arterial intima at the end of the internal carotid artery and the starting points of the anterior and middle cerebral arteries, gradual narrowing of the arterial lumen leading to occlusion, and dilation of the skull base pia mater through the arteries to form a small and dense abnormal vascular anastomotic network. 1 The incidence of MMD exhibits distinct regional and racial characteristics, with higher rates in Asia compared to Europe, America, Africa, and Latin America. Japan is known to have the highest incidence of MMD. A nationwide epidemiological survey conducted in 2003 estimated a prevalence of 6.03 per 100,000 people and an annual incidence rate of 0.54 per 100,000 people. 2 A recent single-center epidemiological study in mainland China included 4128 Moyamoya patients and found a prevalence rate of 0.7651 per 100,000 in Beijing. 3 The incidence of cerebrovascular diseases during pregnancy ranges from 38 to 62.5 per 100,000 deliveries. 4 The incidence of cerebral hemorrhage during pregnancy is 3.5 per 100,000, with a mortality rate of about 18.4%. Among these cases, 10.5% involve pregnant women with MMD. Maternal mortality is closely related to conditions such as preeclampsia, HELLP syndrome, and the timing of diagnosis. 5

The pathogenesis of MMD is not yet fully understood. It is mostly considered to be a nonspecific immunoinflammatory disease that leads to chronic intimal proliferation, smooth muscle cell migration, and stenosis of the terminal intracranial segment of the internal carotid artery, eventually resulting in occlusion. 6 This process forms collateral circulation to supply blood to the brain. The disease primarily affects children and adults. In children, it mainly manifests as insufficient blood supply to the brain, leading to reversible neurological dysfunction, sensory abnormalities, seizures, headaches, and involuntary choreiform movements, with 80.5% of Moyamoya patients experiencing motor function impairment. 7 In adults, the condition predominantly presents as cerebral hemorrhage, including intracerebral hemorrhage, intraventricular hemorrhage, and subarachnoid hemorrhage. Symptoms may include headaches, coma, hemiplegia, and sensory disturbances. At least two-thirds of adult patients present with cerebral hemorrhage as the initial symptom. After the first cerebral hemorrhage, 46% of patients have good recovery of motor function, with a mortality rate of 7%. 8

With the improvement of people’s living standards and the adjustment of fertility policies, there is an increasing trend in the reports of cases of pregnancy complicated with MMD. 9 Whether pregnancy and childbirth will exacerbate the progression of this disease or trigger cerebrovascular accidents, and how to assess the risk of pregnancy and reduce the risk of recurrent cerebrovascular diseases, is particularly important for obstetric medical personnel. 10 In this case series report, we aimed to evaluate the effectiveness of the multidisciplinary approach on the management of pregnant women with MMD. A total of four cases of pregnancy complicated by MMD who were admitted to our hospital between October 2010 and January 2019 were presented.

Case Presentation

Patient history and symptoms: Female, 27 years old, G1P0. The main reason for admission was 32+ weeks of amenorrhea, one-day reduction in fetal movement, and one hour absence of fetal heart rate in the abdomen. She had regular menstruation and weight gain of 10 kg during pregnancy. The patient was diagnosed with primary hypertension 14 years ago and had poor antihypertensive response to oral antihypertensive drugs. The blood pressure was around 130/90 mmHg. Two years ago, during the writing process, she suddenly experienced numbness in my right face and right hand, and her right hand was slightly clumsy in movement. It manifested as unstable holding of a pen, slow writing, no abnormal sensation or movement in my right lower limb, and no unclear speech. The symptoms persisted for about half an hour and resolved spontaneously. Carotid artery ultrasound showed uneven thickening of the right carotid artery intima-media membrane, distal lesions of both internal carotid arteries, bilateral vertebral arteries throughout the entire process (physiological), abnormal origin of the left vertebral artery with course variation, and absence of an unnamed artery.

MMD diagnosis: Transcranial color-coded duplex showed blood flow changes in both hemispheres of the brain consistent with MMD, stenosis of the right middle cerebral artery (severe), stenosis of the right end segment of the internal carotid artery (severe), and occlusive lesion of the left end segment of the internal carotid artery. The head and neck computed tomography angiography showed narrow, multiple stenosis, and occlusion of the bilateral internal carotid artery, anterior, middle, and posterior cerebral artery lumens, accompanied by intracranial capillary formation, suggesting a possibility of MMD. The left vertebral artery formed an autonomous arterial arch with vascular variation. The head magnetic resonance imaging (MRI) showed weakened or disappeared blood flow signals in the intracranial segment of the right internal carotid artery and bilateral middle cerebral arteries on T1WI, multiple tortuous blood vessels in the skull base, basal ganglia, and paraventricular regions, suggesting a possibility of smoke syndrome. Ischemic lesions in the left subcortical area of the frontal lobe and bilateral paraventricular regions and white matter degeneration were also observed. Considering cerebrovascular disease and multiple cerebral artery stenosis, the results of cerebrovascular DSA conducted by the neurology department showed the right anterior cerebral artery, main trunk, and branches of the middle cerebral artery on the right side. The posterior inferior cerebellar artery was not visualized, and the left anterior cerebral artery A1 and middle cerebral artery M1 were occluded further away. Smoke-like vessels around the occluded vessels for compensation were observed. Ultrasound imaging of the left external carotid artery showed that the top branch of the left middle meningeal artery compensated for the blood supply area to the left middle cerebral artery. Due to thinner superficial temporal blood vessels on the same side of the bypass, there was a higher risk of postoperative occlusion. Arterial bypass surgery was not performed. Supplementary Figure 1 includes CT, MRI, and DSA images for Case 1.

After discharge from the neurology department, antiplatelet aggregation drugs, lipid-lowering and antioxidant drugs were regularly taken orally. One year ago, due to pregnancy preparation, aspirin (100 mg, q.d.) was only taken orally, and no discomfort such as dizziness, headache, or limited limb movement occurred again. Two years ago, an examination revealed a thyroid nodule with elevated thyroid-related antibodies. The levels of thyroid-stimulating hormone, free triiodothyronine, and free thyroxine were all normal. The diagnosis was Hashimoto’s thyroid disease, and no special treatment was given. The results of physical examinations were as follows: temperature (T), 37 °C; heart rate (HR): 82 times/min, respiratory rate (RR): 20 times/min; blood pressure (BP): 146/90 mmHg; height (H), 174 cm; weight (W), 78 kg. The general situation was good, and there were no abnormalities in the heart and lungs. The results of the obstetric examination were as follows: The height of the uterine floor was 28 cm, and the abdominal circumference was 93 cm. The head was exposed first, without entering the pelvis or uterine contractions. The fetal heart was not heard, and the measurements outside the pelvis were normal. The results of the vaginal examination were as follows: The uterine opening was not opened, and the head was exposed first. After admission, an intra-amniotic injection of Rivanol was performed to induce labor. A dead female infant was naturally delivered 28 hours after the operation, with a length of 45 cm and a weight of 1600 g. The umbilical cord wrapped around the neck for one week was tight. The fetal skull was soft, and the skin was peeling. No obvious abnormalities were observed in the appearance. Placental adhesions were removed by hand, and postpartum curettage and perineal laceration suturing were performed. Routine postpartum infection prevention was carried out to promote uterine rejuvenation and lactation treatment. The postoperative postpartum woman was generally in good condition and was discharged on the second day. Placental pathology suggested inflammatory changes in the chorioamniotic membrane.

Discharge diagnosis: as fetal death, intrauterine chorioamnionitis, pregnancy with MMD, pregnancy with chronic hypertension (existing), 32+ weeks of pregnancy, G1P1 LOA, natural delivery of newborn umbilical cord around neck for one week, delivery with multiple stenosis of perineal 1 degree laceration, occlusion of bilateral middle cerebral arteries, occlusion of bilateral internal carotid arteries (terminal segment), Hashimoto’s thyroiditis, thyroid nodules.

Patient history and symptoms: Female, 32 years old, G1P0. The main reason for admission was 38+ weeks of menstrual cessation. She had regular menstruation and weight gain of 11 kg during pregnancy. Twenty years ago, due to a headache, we sought medical attention in our hospital and underwent MRI and cerebral angiography. MMD diagnosis: The diagnosis was MMD, but no special treatment was given. After bleeding, she returned to normal without any headache or other symptoms. During pregnancy, there was no discomfort. MRI examination showed bilateral subcortical punctate ischemic lesions, right basal ganglia softening lesions, and abnormal blood flow signals from the right internal carotid artery, middle cerebral artery, and anterior cerebral artery. Supplementary Figure 2 includes MRI images for Case 1. The results of physical examinations were as follows: T, 36 °C; HR, 108 times/min, RR, 20 times/min; BP, 107/66 mmHg; H, 172 cm; W, 82 kg. The general situation was good, and there were no abnormalities in the heart and lungs. The results of the obstetric examination were as follows: The height of the uterine floor was 32cm, and the abdominal circumference was 104 cm. The head was exposed first, entering the pelvis shallowly, without uterine contractions. The measurement outside the pelvis was normal, and the vaginal was not checked. After admission, a lower segment cesarean section of the uterus was performed under epidural anesthesia. The surgical process was smooth, and a female infant weighing 2950 g was delivered alive. The newborn was in good condition, with postpartum bleeding of 500 mL. Routine postoperative prevention of infection, promotion of uterine involution, and breastfeeding of newborns were performed. The postoperative postpartum woman was generally in good condition and then discharged on the 3rd day.

Discharge diagnosis: postpartum hemorrhage pregnancy combined with MMD pregnancy 38+ weeks, G1P1 LOT cesarean section.

Patient history and symptoms: Female, 30 years old, G1P0. The main reason for admission was 39+ weeks of amenorrhea. She had a regular menstrual cycle, with a weight gain of 15 kilograms during pregnancy.

MMD diagnosis: Six years ago, this patient presented with sudden headache and vomiting for three months and was then diagnosed with MMD and cerebral hemorrhage at an external hospital. Supplementary Figure 3 includes non-invasive cerebral vascular ultrasound images for Case 1. She underwent left superficial temporal artery patch surgery and took sodium valproate orally for one month after the surgery. The results of physical examinations were as follows: T, 36.5 °C; HR, 80 times/min; RR, 20 times/min; BP, 123/85 mmHg; H, 172 cm; W, 70 Kg. The general situation of this patient was good, and there were no abnormalities in the heart and lung. The results of the obstetric examination were as follows: uterine floor height, 32 cm; abdominal circumference, 100 cm; head exposed; shallow into the pelvis; no uterine contractions; normal measurements outside the pelvis. The vaginal examination was not performed. After admission, the lower segment cesarean section of the uterus was performed under epidural anesthesia. The surgical process was smooth, and a female infant weighing 3300 g was delivered alive. The newborn was in good condition, with postpartum hemorrhage of 300 mL. Routine postoperative prevention of infection, promotion of uterine involution, and breastfeeding of the newborn were performed. The postoperative mother was generally in good condition and discharged on the 3rd day.

Discharge diagnosis: postoperative Moyamoya disease (left superficial temporal artery application), history of cerebral hemorrhage, placental adhesion, pregnancy 39+ weeks, G1P1LOT cesarean section.

Patient history and symptoms: Female, 41 years old, G3P1. The main reason for hospitalization was cessation of pregnancy after 8+ weeks of amenorrhea. Twelve years ago, due to amniotic fluid contamination, a lower segment cesarean section was performed in an external hospital. Four years ago, due to vomiting and coma, she sought medical attention from a neurology department in another city and underwent MRI and cerebral angiography examinations.

MMD diagnosis: The diagnosis was MMD and cerebral hemorrhage. Due to a small amount of bleeding, she underwent conservative treatment and recovered. The results of physical examinations were as follows: T, 36.5 °C; HH, 80 times/min; RR: 20 times/min; BP: 110/70 mmHg; H, 148 cm; W 46 kg. Double diagnosis was made: anterior position of the uterus, enlarged as at 8+ weeks of pregnancy, with no abnormalities in both appendages. The ultrasound showed an intrauterine fetal sac of 4.2 × 1.5 cm, a gestational bud length of 1.2cm, and reachable to the original cardiac tube for pulsation. After admission, painless negative pressure suction surgery was performed under general anesthesia, and postoperative routine prevention of infection promoted uterine involution. The postoperative patient was generally in good condition and discharged on the first day.

Discharge diagnosis: early pregnancy with moyamoya scar uterus.

Diagnostic Criteria for MMD

The diagnostic criteria for MMD include (1) DSA findings: This imaging technique reveals the following: stenosis or occlusion at the terminal portion of the internal carotid artery and/or the initial segments of the anterior cerebral artery and/or middle cerebral artery. Additionally, an abnormal vascular network at the base of the brain appears in the arterial phase. These findings may be bilateral or unilateral, with possible different stages of disease on each side. (2) MRI and MRA findings: MRI and MRA scans show stenosis or occlusion at the terminal portion of the internal carotid artery and/or the initial segments of the anterior cerebral artery and/or middle cerebral artery. An abnormal vascular network in the basal ganglia region is indicated by more than two clear flow voids in the basal ganglia area on a single scan layer. These findings are typically bilateral, though the stages of disease may differ on each side. (3) Exclusion of associated diseases: To confirm a diagnosis of MMD, the following conditions must be excluded: cerebral atherosclerosis, autoimmune diseases (such as systemic lupus erythematosus, antiphospholipid antibody syndrome, polyarteritis nodosa, and Sjögren’s syndrome), meningitis, neurofibromatosis, intracranial tumors, Down syndrome, head trauma, radiation injury, Turner syndrome, Alagille syndrome, Williams syndrome, Noonan syndrome, Marfan syndrome, tuberous sclerosis, congenital megacolon, type I glycogen storage disease, Prader-Willi syndrome, Wilms’ tumor, oxalate deposition disease, sickle cell anemia, Fanconi anemia, spherocytosis, eosinophilic granuloma, type II fibrinogen deficiency, leptospirosis, pyruvate kinase deficiency, protein deficiency, myofibromatosis, osteogenesis imperfecta, polycystic kidney disease, oral contraceptive use, and drug intoxication (such as cocaine).

Pregnancy Risk Assessment of MMD Patients of Childbearing Age

MMD is a chronic and progressive cerebrovascular disease, characterized by gradually worsening stenosis and occlusion of the main arteries in the anterior circulation, abnormal compensatory vascular network hyperplasia in the skull base, continuous enhancement of posterior circulation compensation, and compensatory phenomena in the external carotid artery. 11 MMD can be divided into two types: ischemic type and hemorrhagic type. 12 Hemorrhagic type is an important type of MMD, mainly occurring in adults, while ischemic type MMD is more common in children. 13 The severity of these diseases cannot be underestimated and requires our high attention and timely treatment.

MMD during pregnancy can be divided into three types: those discovered before pregnancy, those that occur during pregnancy, and those that occur after childbirth. 14 According to the 2017 MMD diagnosis and treatment consensus, digital subtraction angiography (DSA) and MRI/MRA examination are the main diagnostic methods for MMD. 15 Through these examinations, it can be found that I. the end of the internal carotid artery and/or the anterior cerebral artery and/or the starting segment of the middle cerebral artery are narrow or occluded; II. abnormal vascular network at the skull base appears in DSA arteries or abnormal vascular network appears in the basal ganglia area in MRA; III. the above manifestations are bilateral, but the staging of the lesion may vary. If all the above manifestations are met, and other secondary factors (atherosclerosis, autoimmune diseases, meningitis, brain tumors, Down’s syndrome, neurofibromatosis, cranial trauma, radiation head irradiation, etc.) are excluded, the disease can be diagnosed. In this case report, MMD was diagnosed through pre-pregnancy, previous MRI, and/or head and neck computed tomography angiography.

Whether pregnancy increases the risk of cerebrovascular disease in patients with MMD is not yet determined. 14 Pregnant age MMD patients should undergo a pregnancy risk assessment by a joint obstetrician and neurologist before pregnancy. The medical history should be inquired in detail, such as whether there are risk factors for cerebrovascular disease (eg, family history, smoking history, drinking history, labor intensity, sleep disorder, hypertension, diabetes, hyperlipidemia, hyperhomocysteinemia, hyperuricemia, and hypohemoglobin). The clinical symptoms (eg, asymptomatic, dizziness, headache and vomiting, muscle weakness, sensory disorders, visual disorders, language disorders, and consciousness disorders) and signs of having a history of bleeding and performing auxiliary examinations to determine the cerebral vascular dynamics should also be considered. All four patients in this report were diagnosed with MMD before pregnancy, with obstetrics as the leading factor. Under the collaborative model of multiple disciplines such as neurology, neurosurgery, and imaging, combined with clinical symptoms, cerebral perfusion, and metabolic data, the condition was comprehensively judged, and pregnancy risks were fully communicated with patients and their families.

Pregnancy Management and Treatment of Pregnant Women with MMD

The French MMD clinical practice guidelines indicate that the risk of complications in pregnancy and perinatal MMD is currently unclear, and it seems that cerebrovascular complications have not significantly increased until delivery. 16 During the perinatal period, the reported complications (cerebral hemorrhage and TIA) are mainly related to patients who have not yet been diagnosed with MMD. Pregnant women with MMD during pregnancy are clearly diagnosed before pregnancy, and regular prenatal examinations are conducted during pregnancy while closely observing the function of cerebral blood vessels. The most common complication during pregnancy is cerebral hemorrhage, especially when the gestational age is greater than 24 weeks, postpartum cerebral infarction is the most common. 9 Pregnancy treatment is challenging and requires multidisciplinary collaboration, considering the probability of bleeding and rebleeding, as well as the complexity and risk assessment of cerebral blood vessels. 17 During pregnancy, blood pressure should be regularly monitored, especially for pregnant women who undergo strict and regular self-monitoring to maintain stable blood pressure. If necessary, antihypertensive and spasmodic treatment should be carried out. Actively controlling hypertension in pregnant women has become an important measure for preventing stroke.

Different Methods of Termination of Pregnancy and Anesthesia Management

The multidisciplinary collaborative model is a new diagnostic and treatment model that emphasizes patient-centered approach, with team members working closely together to develop targeted intervention plans tailored to the needs of patients and improve the treatment effectiveness of patients during the perioperative period. 18 There is currently no consensus on the optimal delivery method for pregnant women with MMD. The timing and method of delivery should be comprehensively considered based on the location, severity, and gestational age of cerebral vascular lesions in MMD patients. Negative pressure suction surgery should be used in early pregnancy. 19 Unless the cause of cerebral hemorrhage is relieved, drug-induced labor should not be used in mid pregnancy. 20 For example, mifepristone plus Misoprostol should not be used for induced labor in patients with thrombosis or hypertension. Intraamniotic injection of Rivanol can be used for induced labor, which has a high success rate and is relatively safe. 21 When deciding on the way to terminate pregnancy in late pregnancy, patients, neurologists, obstetricians, and anesthesiologists need to make a joint decision. Cesarean section has a short time and high controllability, which can effectively control blood circulation stability, maintain normal levels of carbon dioxide in the blood, and maintain appropriate fluid balance. 22 There are also studies suggesting that vaginal delivery is not associated with excessive occurrence of cerebrovascular complications. 23 Takahashi et al 24 also found that the safe delivery rate for pregnant women, with MMD undergoing vaginal natural delivery after epidural anesthesia is 74.1%. If the labor process progresses smoothly and the mother’s condition is stable, the vaginal trial can be strictly monitored.

Our hospital has an incidence rate of 98.1 per 100,000 deliveries for pregnancy-related stroke, with extensive experience in treatment. When patients present symptoms such as headaches, vomiting, or limb numbness, the possibility of concomitant neurological disorders should be considered. Therefore, for pregnant women with a history of moyamoya disease, in addition to monitoring the risk of recurrent cerebrovascular accidents during pregnancy, attention should also be given to the occurrence and progression of late obstetric complications. Proactive prevention and management are crucial, necessitating enhanced prenatal care with increased frequency of antenatal visits to improve maternal and neonatal outcomes.

Conclusions

In conclusion, patients with MMD have impaired cerebral hemodynamics, decreased cerebrovascular reactivity, and impaired cerebral blood flow self-regulation ability, which can exacerbate ischemic cerebral perfusion insufficiency. Pregnancy complicated by cerebrovascular diseases has high mortality and disability rates, posing a serious threat to the safety of both mother and baby. It requires joint attention from obstetricians and neurologists to ensure early diagnosis and proper treatment. When a patient exhibits symptoms such as headache, vomiting, or limb numbness, the possibility of concurrent neurological disorders should be considered. If there is suspicion of cerebral hemorrhage or cerebral infarction, a CT scan should be the first choice. For patients with MMD, DSA remains the most accurate method for diagnosing cerebrovascular diseases. However, due to its invasive nature and high technical demands, it is not the preferred initial method. For patients with coexisting cerebrovascular malformations, hematological, and cardiovascular diseases, focused monitoring and management through multidisciplinary collaboration are essential. Any neurological symptoms should prompt immediate attention from doctors, with early diagnosis and appropriate treatment based on imaging studies. Selecting the appropriate method and timing for terminating the pregnancy is crucial to improving maternal outcomes and enhancing the quality of life for patients. Further prospective investigations are needed to validate the findings observed in these cases.

Data Sharing Statement

The original contributions presented in the study are included in the article. Further inquiries can be directed to the corresponding author.

Ethics Approval and Informed Consent

Written informed consent was obtained from the patients. We have received Xuanwu Hospital Capital Medical University’s ([2017]021) approval to publish the case details.

Consent for Publication

Consent to publish was obtained from the patients.

This work was supported by the Undergraduate Innovation Project at Capital Medical University (XSKY2022238).

The authors declare that they have no competing interest in this work.

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• Data Descriptor
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• Published: 24 August 2024

A benchmark for 2D foetal brain ultrasound analysis

• Mariano Cabezas   ORCID: orcid.org/0000-0002-4417-1704 1   na1 ,
• Yago Diez 2   na1 ,
• Clara Martinez-Diago 3   na1 &
• Anna Maroto 3   na1  

Scientific Data volume  11 , Article number:  923 ( 2024 ) Cite this article

Metrics details

• Scientific data

Brain development involves a sequence of structural changes from early stages of the embryo until several months after birth. Currently, ultrasound is the established technique for screening due to its ability to acquire dynamic images in real-time without radiation and to its cost-efficiency. However, identifying abnormalities remains challenging due to the difficulty in interpreting foetal brain images. In this work we present a set of 104 2D foetal brain ultrasound images acquired during the 20th week of gestation that have been co-registered to a common space from a rough skull segmentation. The images are provided both on the original space and template space centred on the ellipses of all the subjects. Furthermore, the images have been annotated to highlight landmark points from structures of interest to analyse brain development. Both the final atlas template with probabilistic maps and the original images can be used to develop new segmentation techniques, test registration approaches for foetal brain ultrasound, extend our work to longitudinal datasets and to detect anomalies in new images.

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Background & summary.

Foetal brain development is a complex sequence of events ocurrying throughout gestation. From early stages of embryonic development, the brain undergoes structural changes until several months after birth 1 , 2 . Therefore, understanding normal brain development is essential to identify potential deviations which may lead to neurological disability. Specifically, various studies have described normal milestones within a specific chronology 3 , 4 , 5 . These changes can be observed by experts in prenatal diagnosis with skills in foetal neurology using ultrasound (US) and magnetic resonance imaging (MRI). However, identifying neurodevelopmental deviations is challenging due to the difficulty in image interpretation 5 .

Currently, US is the established technique for screening due to its ability to acquire dynamic images in real-time without radiation and cost-efficiently. The international guidelines recommend the acquisition of a routine first trimester US within the 11th - 14th weeks and a mid-trimester scan within the 19th - 22th weeks of gestation for anatomical evaluation of the foetus 6 . The standard foetal assessment includes the evaluation of planes acquired using 2D-US. Even though 3D-US is considered useful for prenatal diagnosis of some disorders (mainly involving the face, the skeleton, the cardiovascular system or the brain), the major obstacles for 3D-US implementation worldwide as the main routine acquisition type are related to foetal motion artefacts and acoustic shadowing during volume acquisition. Another widely used prenatal imaging technique is MRI. However, MRI is not used as a primary screening tool and is instead used as a complementary acquisition when foetal abnormalities are suspected (even in selected high-risk cases) 7 , 8 . Moreover, foetal MRI performed before the 18th-22nd weeks does not usually provide additional information to that obtained by US. Generally, MRI provides a detailed visualization of structures between the 26th and 32nd weeks, being superior to US and less susceptible to limitations from maternal body conditions and foetal presentation (bones do not produce occlusion artefacts in MRI) 8 . Within this context, a foetal brain US atlas based on 3D scans of healthy foetuses was recently published 9 . This atlas demonstrates the feasibility of assessing structural changes in the cortex and in the subcortical grey matter by US. Furthermore, this chronological US-based atlas of the foetal brain at each gestational age has the potential to become a useful tool to detect development abnormalities when combined with the standard planes of mid-trimester routine scans. However, considering that the primary diagnostic tool in pregnancy remains 2D-US, studies aimed at improving the identification of fetal structures should focus on 2D-US.

As there is a degree of variability in the shapes of anatomical regions between individuals, atlases are typically built by taking into account a number of images considered to fall within normal parameters. A crucial step in this process is finding corresponding regions between different images and warping them to a common space, a process known as image registration. In the case of US atlases, the lower signal-to-noise ratio (SNR), the differences in location for the foetuses due to the lack of a robust localization technique and the presence of image artefacts that may blur or shadow salient features and structure boundaries makes this process particularly challenging.

In this paper we present a set of foetal brain 2D-US images with manual landmark annotations of structures of interest and soft probabilistic maps for those structures based on these landmarks in a common space. The aim of this dataset is to provide a set of US images as a starting point to study registration and segmentation of foetal brain scans and provide tools for researchers focusing on foetal brain development. Furthermore, in combination with the recently published 4D atlas, this dataset can be also used to study 2D to 3D US registration and techniques to determine the “real age” of gestation and potential abnormalities when comparing to the atlas. To define a common space, a registration algorithm based on fitting an ellipse to the skull segmentation of a convolutional neural network (CNN) was used to align all the images to a common space. In order to avoid misalignements caused by image quality, a subject ellipse was used to estimate an affine transformation to a common (atlas) space. We also took advantage of the automatic differentiation capabilities of the pytorch package in three fundamentally different optimization settings (training a CNN for segmentation, fitting an ellipse to a segmentation boundary, and estimating an affine transformation).

In order to create the dataset presented, the data collected was processed as follows: First, the skull was automatically segmented using a UNet network, then an ellipse was automatically fitted to the shape of the skull. These ellipses where used to register each image to a reference image. Soft probabilistic maps where built using the set of registered images. The rest of this section includes details on each of these steps and a summary of other publicly available datasets. A visual summary can be found in Fig.  1 .

Methodology: 1) The skull is automatically segmented using a UNet network (top-left). 2) An ellipse is fitted to the skull segmentation (top-right) 3) to estimate an affine transformation to a reference image (bottom-right). The axes of the fitted ellipse are warped to the image coordinate axes and are re-scaled to fit the ellipse in the reference image (bottom-left).

Ultrasound data

A prospective cohort of low-risk pregnant women was recruited at routine mid-trimester foetal ultrasound scan. All participants initiated antenatal care before the 12th weeks of gestation, underwent the first trimester ultrasound scan between 12th and 14th weeks and had a low risk for aneuploidies in the first trimester combined screening. Written informed consents were obtained from participants. A private dataset of 70 pregnant women with a routine mid-trimester foetal ultrasound scan at [20 ~ 20.6] weeks without detected abnormalities was acquired, totalling 104 scans (8 women were scanned three times, 18 women were scanned twice and the remaining 44 women were only scanned once). The median of the maternal age was 31 (range 18-42). Images were acquired using high-frequency transabdominal probe (C2-9) of Voluson E10 ultrasound system. For each subject, a transverse view of the foetal head demonstrating a standard normative transcerebellar scanning plane was manually annotated by2 trained clinical experts (Fig.  1 top right). Both experts were part of the Prenatal Diagnosis Unit, one with over 10 years of experience and the other with 5 years of experience. The experts jointly participated in the annotations of each imageto highlight common structures related to brain development as follows:

Skull : 4 landmarks from the inner line of the skull were annotated: 2 at the level of the middle line and the other 2 in a perpendicular imagined line at the level of the posterior corners of the cavum septi pellucidi (CSP).

Cerebellar peduncles (Thalami) : 1 landmark marking the edges of both thalami at the middle line and the outer edges of the concavity shape were annotated (3 total points).

Cerebellum : 8 landmarks on the perimeter the cerebellum were annotated. Specifically, 2 points from the midline, 2 points from the cerebellum external edges and 4 points in the middle of each cerebellum hemisphere.

Cavum septi pellucidi (Cavum) : 4 points, each marking one corner of its rectangular shape, were annotated.

Sylvian Fissure (Sylvius) : 2 landmarks, one for each sylvian fissure edge, and 1 landmark in the inflection point of the fissure were annotated. For all the images, only the inferior fissure was visible.

Midline : 1 landmark in the upper edge of the midline and 1 landmark in the upper edge of the CSP were annotated.

An important aspect of acquisition is that the sylvian fissure was always scanned on the lower part of the image, irrespective of the head orientation (left to right or right to left). This phenomena has important implications for registration. When aligning all images to a common 3D space (for example a 3D atlas template) in order to have all images facing the same direction, the transformation can be modeled with 180° rotations over the y axis. If the transformation is limited to the 2D space (image coordinates), a mirroring operation has to be applied to align all images. In the code we provide to process the images, the second option is used for simplicity. Furthermore, our common space is oriented from left to right (anterior to posterior).

Data acquisition was approved by the ethics committee “Comitè d’Ètica d’Investigació amb Medicaments CEIM GIRONA” with the code 2023.067. Furthermore, the subjects were informed and consented to the open publication of the data.

Skull segmentation database

The segmentation dataset used to train a skull segmentation CNN was downloaded from the HC18 grand challenge on “automated measurement of foetal head circumference using 2D ultrasound images” 10 , 11 . The challenge comprises a set of 800 × 540-pixel 2D US images with a pixel sizes ∈ (0.052, 0.326) mm. The data set was split into 999 images for training and 335 for testing. For each image in the training set, an ellipse was manually fitted to the HC by a trained sonographer but precise segmentations of the true skull boundary were not provided. No pre-processing techniques were applied to the images apart from computing the z-score of the intensity values with respect to the mean and standard deviation of the whole image (non-0 intensities) before feeding them to the segmentation network. The network trained with all the training set images was then used to roughly segment the skull of our own 2D US images and provide a starting point to fit an ellipse.

Other public databases

To the best of our knowledge, only 3 other large datasets focusing on 2-D ultrasound have been made publicly available, including HC18. As mentioned on our brief description of HC18, the annotations are limited (only an ellipse roughly representing the skull is given), the subjects present a large distribution of gestational ages and no further information on the acquired plan e is provided. For studies focusing on the segmentation of structures of interest or registration, new annotations would be needed. Furthermore, the gestational age and acquisition plane for each subject can have a large impact on the appearance of the structures. Another public dataset presented by Burgos-Artizzu et al . 12 includes a large set of images (12400) ranging from the 18th to the 40th week of pregnancy. Images were acquired using six different machines and labelled at the image level. Similarly to HC18, the dataset presents a large range of gestational ages and limited annotations that could only be used to develop classification algorithms. Finally, Alzubaidi et al . 13 released a public dataset of 3832 high resolution images. In contrast with the other two datasets, no mention of gestational age is provided and once again rough annotations in the form of bounding boxes are provided. Moreover, the authors also highlight image resampling as an additional shortcoming of their dataset.

In our dataset, we focus on a specific acquisition plane and gestational age as defined by international guidelines and raw images are provided. Furthermore, landmarks for the most salient points of each structure of interest are provided with software tools to estimate finer-grained masks and bounding boxes around the landmarks. In that sense, our dataset provides a useful tool to address multiple image analysis problems including registration that could not be easily approached with other available datasets and no additional annotations.

Registration method

Medical image registration 14 , 15 is a necessary initial step for many medical image processing applications that rely on group-wise analysis. Typically, images are registered in pairs: one of them is defined as the “fixed” image (or reference) and the other as the “moving” image. The moving image is then warped using a transformation function to generate the final “moved” image. The transformation is commonly optimised using a predefined metric that computes image similarity between the reference and the moved image after transformation. Here, we present a coarse registration method to roughly align different foetal ultrasound images as described in the following sections and illustrated in Fig.  1 . We chose one of the images as the common “reference” image (image 10) and registered the remaining images to it.

Automatic Skull segmentation using a Unet

The Unet architecture 16 is one of the most common CNN architectures for image segmentation. Due to its encoder-decoder structure and the use of skip connections, precise segmentations based on multi-scale features can be obtained for a variety of segmentation applications 17 . Consequently, we used a 2D Unet trained on the HC18 challenge dataset to provide a rough segmentation of the skull for all the images in our registration dataset (see Fig.  1 for an example). Specifically, the encoder and decoder blocks are comprised of 6 convolutional layers with a residual connection 18 of 32, 32, 128, 256, 256 and 1024 features each (inverse order for the decoder) and a bottleneck of 1024 features. To optimise the weights of the Unet, the Adam algorithm with default initial learning rate was used to minimise the binary cross-entropy loss.

Ellipse Registration

An ellipse is a planar curve representing the locus of the points with constant added distances to two “focal points”, as expressed by the quadratic equation:

With points that satisfy f E ( X ,  Y ) ≠ 0 being inside the ellipse perimeter ( f E ( X ,  Y ) < 0) or outside of it ( f E ( X ,  Y ) > 0). The general equation’s coefficients can be obtained from known semi-major axis a (represented by the magnitude of the turquoise vector in Fig.  1 ), semi-minor axis b (represented by the magnitude of the cyan vector in Fig.  1 ), centre coordinates ( x 0 ,  y 0 ) (represented by the point where the two vectors meet in Fig.  1 ) and rotation angle θ (the angle from the positive horizontal axis to the ellipse’s major axis as observed in Fig.  1 ) using the formulae:

These expressions can be derived from the canonical equation \(\frac{{x}^{2}}{{a}^{2}}+\frac{{y}^{2}}{{b}^{2}}=1\) by an affine transformation of the coordinates ( x ,  y ) (with a translation (− x 0 , − y 0 ) and an angle θ ).

Given the set of pixel coordinates of the skull segmentation ( \(({X}_{skull},{Y}_{skull})=\,[({x}_{1},{y}_{1}),\ldots ,({x}_{N},{y}_{N})]\) ) we can fit an ellipse using its parameters ( a , b , x 0 , y 0 and t h e t a ) by minimising the following objective function:

where the coefficients A to F are substituted in f E by their definitions in equations ( 2 ) to ( 7 ) and the estimated ellipse parameters.

This process is repeated 5 times, removing erroneous points of the skull segmentation mask that are one standard deviation away from the mean ellipse error according to Eq. ( 10 ). With the parameters of the skull ellipse estimated through optimisation, we can now define an affine transformation (referred to as Ellipse from now on) to move the brain to the centre of the image as:

Affine image registration

For comparison, a regular rigid registration of 6 unrestricted parameters was performed with different initialisations. From the most basic identity initialisation (referred to as Affine ), to an initialisation using the ellipse parameters of the reference image (referred to as Affine (Reference ellipse) ) and a refinement of the ellipse-based affine transformation from Eq. ( 11 ) (referred to as Ellipse + Affine ).

Probabilistic maps

Once the images are co-registered to a common space based on their ellipse, a two-step process is performed to generate probabilistic maps for all the structures with more than 2 landmarks.

First, the concave hull of each structure is computed using the alphashapes package. This concave hull represents a rough segmentation of the location of the structure. Second, the segmentations for all the subjects are averaged per structure to determine the probability of each pixel to belong to that structure.

This approach has some limitations. Namely, some structures have a polygonal shape, even though they are actually curves (e.g. sylvius) and the final masks are only a rough representation of the real boundaries (e.g. cerebellum). However, these polygonal maps can be still used to determine growth milestones and to provide a rough location of the structure of interest.

Data Records

The original images with manual landmark annotations (Gimp image editing tool format) and the co-registered images and probabilistic maps used within this paper can be found on figshare 19 , and are organised with subject id number (1-52) and an additional number for multiple scans (e.g. 36 and 36.1). Co-registered images are saved in JPEG format with the “_registered” suffix. The final probability maps estimated using a combination of co-registered landmarks and the alphashape package are provided as JPEG images with the name of the structure (e.g. sylvius.jpeg), while comma separated value (CSV) files with the point landmarks of all registered subjects are compressed into a single zip file.

In total, the released dataset consists of 104 annotated 2D US images of foetal brains on the 20th week of pregnancy. The manual annotations are described in Ultrasound dataset section.

Technical Validation

To validate the techniques used for co-registration to a common space, we focused on common medical imaging metrics for registration using landmarks. In this section we describe these metrics and provide some qualitative and quantitative results of the alignment (including a visualisation of the probabilistic maps of one of the structures of interest).

Regarding the quality of the US images, all images were acquired with a high frequency ultrasound probe (2-9 MHz) that provides high resolution images following the ISUOG recommendations. The most constraining factor for the quality of the ultrasound images is maternal obesity. However, for this study we excluded women with maternal morbid obesity (body mass index > 40) as it is one of the factors for high-risk pregnancy. To further illustrate that point, we provide a comparative example between an image from the dataset and a lower quality one in Fig.  2 .

Qualitative comparison between a low quality image where structures are not clearly visible and and image from the dataset.

Evaluation metrics

For this study we chose to use the anatomical knowledge defined by expert annotations as the main directive to evaluate the quality of the registration and avoid focusing exclusively on common pixel-metrics that might be unreliable and disconnected from physical properties 20 . Specifically, we used the point annotations described in the Ultrasound Data section with two point-based metrics and one area-based metric for every anatomical structure with more than 2 points (all the structures except the midline). For completeness sake, we also included the structural similarity index metric (SSIM) pixel-based metric.

Point-based metrics

In order to penalise partial matches between anatomical structures, we considered the Hausdorff distance ( d H ), that computes the worst possible Euclidean distance ( d ( p i ,  p j )) between two sets of points P f (| P f | =  N ) and P m (| P m | =  M ). We also considered the average of the minimum Euclidean distances ( d E ) to express global similarity between structures defined by landmarks.

Area-based metric

To evaluate the superposition between two anatomical structures defined as 2D landmarks (points), we first computed their concave hulls and then considered their Dice similarity coefficient (polygon DSC).

Image similarity metric

For completeness, we also considered the structural similarity index measure (SSIM) as a pixel-intensity-based metric.

Comparison of coarse registration approaches

Figures  3 , 4 and 5 summarise the results with boxplots and Wilcoxon signed-rank tests for all the registration methods and metrics considered. Wherever possible, the results for different anatomical areas are presented separately. For the Euclidean and Hausdorff metrics, lower values indicate better registration, while for the SSIM and Dice metric higher results indicate better registration. Moreover, a qualitative example to illustrate misalignments between the reference points and the registered landmarks is provided in Fig.  6 .

Quantitative results for all the methods on each structure (Hausdorff distance, d H , lower values indicate better registration). The upper part of each boxplot figure indicates the results of pairwise statistical Wilcoxon tests: (ns: 5.00e-02  < p ≤ 1.00e+00, * 1.00e-02  < p ≤ 5.00e-02, ** 1.00e-03  < p ≤ 1.00e-02, *** 1.00e-04  < p ≤ 1.00e-03, **** p ≤ 1.00e-04).

Quantitative results for all the methods on each structure with multiple points (polygon DSC, higher values indicate better registration). The upper part of each boxplot figure indicates the results of pairwise statistical Wilcoxon tests: (ns: 5.00e-02  < p ≤ 1.00e+00 * 1.00e-02  < p ≤ 5.00e-02, ** 1.00e-03  < p ≤ 1.00e-02, *** 1.00e-04  < p ≤ 1.00e-03, **** p ≤ 1.00e-04).

Quantitative results for all the methods according to the SSIM metric (higher values indicate better registration). The upper part of each boxplot figure indicates the results of pairwise statistical Wilcoxon tests: (ns: 5.00e-02  < p ≤ 1.00e+00, * 1.00e-02  < p ≤ 5.00e-02, ** 1.00e-03  < p ≤ 1.00e-02, *** 1.00e-04  < p ≤ 1.00e-03, **** p ≤ 1.00e-04).

Qualitative example of the alignment between the reference image and a randomly selected subject (11). The background image corresponds to the warped image after registration, circles denote the reference points for each structure, crosses represent the registered points and lines are used to illustrate misalignment between the reference and the registration.

Regarding point metrics, the ellipse ( E ) and ellipse with affine methods ( E+A ) obtain overall better results than the other methods. In general, the differences observed were found to be statistically significant for both point metrics and most anatomical structures. Exceptions to this are the thalami and the cerebellum where the pixel based affine registration method initialised using the reference ellipse ( AFF+I ), obtains results that appear worse but are not significantly different. Comparing the E and E+A methods, small (and not statistically significant) differences can be observed. Using a refinement registration after ellipse-based method slightly worsens the metrics when applied to the skull but improves them in all other anatomical structures. This is an expected result as the main focus of the first method is to co-register the skulls (ellipses). The uninitialised affine transformation ( AFF ) obtains significantly worse results than these two methods and has a higher variance of values as illustrated by its wide boxplots. Both methods using exclusively pixel-wise affine registration (AFF, AFF+I) achieve results that are worse than the metrics of the original moving image in some cases. This illustrates the disconnect between pixel-based metrics guiding these methods and point-based metrics targeting distances between real anatomical structures (especially for noisy sequences).

Regarding the differences between the Euclidean and Hausdorff metrics (especially the median values shown by the central line in boxplots), slightly higher Hausdorff values indicate that some point pairs are further than the average euclidean distance mean value. This is especially noticeable on the skull for E and A+E and the thalami for AFF .

The other two metrics show the same general tendencies, even though they focus on different aspects of the registration. The low SSIM values observed for all methods (even though E and A+E outperform all methods) illustrats how challenging this registration scenario is. The variations between individuals and acquisitions and low SNR make the intensity values particularly unreliable. On the other hand, the high anatomical DSC results observed for the ellipse-based methods (includding AFF+I) validate our geometric approach that relies on a rough initial skull estimate to determine the general shape and orientation of the brain. Similarly high results obtained for the cerebellum indicate that a correct skull placement is a crucial important step towards the registration of all brain structures.

Finally, Fig.  7 shows the final heatmap generated from the registered concave hulls (E+A) of the cerebellum for all output images. Even though faint outlines of some incorrect registration results outside of the cerebellum region (delimited by orange points) can be observed, the higher probability regions in the heatmap clearly correspond to the cerebellum region of the reference image delimited by the manually annotated orange landmarks.

Probabilistic map for the cerebellum structure based on the averaged concave hull of the landmarks for each image. Landmarks for the reference image (background) are also provided.

Usage Notes

The code provided to analyse the images and perform a rough initial alignment to a common space has been developed using python. A set of Jupyter notebooks detailing the use of each step is also provided in the repository with visualisation examples of each step of the processing pipeline. Furthermore, we provide the trained weights for the skull segmentation network as part of the data records (file unet.pt 19 ).

Regarding the use of python packages, the code heavily relies on pytorch (version 1.12.0 with CUDA 10.2) to do the heavy lifting. However, numpy (version 1.21.6), scipy (version 1.7.3), scikit-learn (version 1.0.2), scikit-image (version 0.18.1), pandas (version 1.3.4), persim (version 0.3.1) and alphashape (version 1.3.1) are also used for some of the processing steps or to analyse different metrics related to the registration. Furthermore, opencv-python (version 4.5.2.52) and gimpformats (version 2021.1.4) where used to open the images with python. In particular, manual landmark annotation where done using the Gimp software and were stored (together with the ultrasound image) using the xcf format. Finally, matplotlib (version 3.7.1), seaborn (version 0.11.0) and statannot (version 0.2.3) were used for results visualisation inside the Jupyter notebooks.

Code availability

All the code used in the study to generate the final atlas and to co-register the images is publicly available at https://github.com/marianocabezas/fetal-brain .

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These authors contributed equally: Mariano Cabezas, Yago Diez, Clara Martinez-Diago, Anna Maroto.

Authors and Affiliations

Brain and Mind Centre, University of Sydney, Sydney, Australia

Mariano Cabezas

Faculty Of Science, Yamagata University, Yamagata, Japan

Hospital Universitari de Girona Doctor Josep Trueta, Girona, Spain

Clara Martinez-Diago & Anna Maroto

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All authors conceived and designed the experiments, C.M. and A.M. collected the images and performed the landmark annotations, M.C. and Y.D. conducted the experiments and analysed the results. All authors reviewed the manuscript.

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Correspondence to Mariano Cabezas .

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Cabezas, M., Diez, Y., Martinez-Diago, C. et al. A benchmark for 2D foetal brain ultrasound analysis. Sci Data 11 , 923 (2024). https://doi.org/10.1038/s41597-024-03774-3

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Received : 27 December 2023

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Published : 24 August 2024

DOI : https://doi.org/10.1038/s41597-024-03774-3

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