You might have heard of a baby being in the posterior position.
This fetal position is also known as the OP or ‘back to back’ position.
Some people even refer to this as the ‘sunny side up’ position.
All these terms refer to the same position – the occiput posterior fetal position.
Some people assume, as long as the baby is head down, the way the baby is facing doesn’t affect how they give birth.
However, the fetal position doesn’t need to be a transverse position (side-lying) or a breech position (bottom down) for it to be considered a fetal malposition.
Let’s start from the most common position babies adopt during the last stages of pregnancy.
When most babies enter the pelvis head down, the baby’s chin is touching his chest. This position helps the crown of the head enter the pelvis first so the head can mold to fit through the pelvis.
Remember, the skull of a baby isn’t fused, so the bones can shift, to allow them to be squeezed through the birth canal.
You might like to read more in What Happens To Your Baby’s Head During Birth?
The optimal position the baby adopts is the occiput anterior position (OA position). The baby enters the pelvis with his back and occiput (the back of the head) towards his mother’s front. Some healthcare professionals will simply refer to an anterior baby.
As a rule to remember try to think of the ‘A’ position as the optimal one and the ‘P’ for ‘poor’ position.
Posterior baby position
The baby enters the pelvis in an occiput posterior position when his back is spine to spine with the mother’s.
You might think there’s not a big difference between anterior and posterior fetal positions. But human beings are the only terrestrial mammals that walk on their hind limbs, which makes that pelvic space quite tight, and every millimeter counts when giving birth.
The occipito-posterior fetal position means that the baby’s head is angled, so it measures larger. The top of the head is entering the pelvis and doesn’t mold as well as the crown. The spine is also extended rather than curled, which also prevents the crown from entering the pelvis first.
Most babies who enter the pelvis in an OP position will eventually turn to the OA position for birth, especially if they aren’t the first ones to go through that pelvis.
Some babies will be born in the occiput posterior position, but this can mean labor is slower and more painful.
At other times, especially for first-time mothers, a baby in the OP position can’t be born and will need the help of an ob-gyn doctor.
Posterior baby symptoms
There are several signs to indicate which position your baby is in.
Here are five things to look out for, which can help you find out whether your baby is in the occiput posterior position:
#1: Posterior baby belly shape
In an occipito-anterior position (considered the ideal position), the back of the baby is right behind the mother’s belly, giving her abdomen the usual round, solid appearance.
In a posterior position, the baby’s back is towards the mother’s back, so her pregnant belly has an odd-looking shape.
The baby’s limbs, especially his hands and knees, are at the front, and shape the woman’s belly. It might look flattened instead of its usual pregnant round shape.
The woman’s belly button might dip and the overall pregnant abdomen could feel more squishy and bumpy.
#2: Posterior position baby kicks
A woman pregnant with an OP baby might feel baby’s kicks and movements more to the front as baby’s hands and knees are moving right under her belly’s skin.
#3: Feel for your baby’s position
Feeling for your baby’s position is something any pregnant woman can do, especially during the third trimester, when the baby is bigger and body parts are more easily identifiable.
Place one of your hands flat on the side of your belly. Then, with the other hand and fingers, try to feel through the abdominal wall.
Your baby’s back should feel quite firm and solid. If you feel many bumps and hollow spaces, you’re most likely feeling the baby’s front.
#4: Baby’s heartbeat
If you own a doppler, or during your prenatal visits when your midwife listens to your baby’s heartbeat, it’s easier to find a muffled heartbeat almost anywhere in your belly if the baby is in a posterior position.
It will be more difficult to find a loud, clear heartbeat, though, as the doppler won’t be applied to the baby’s body directly, but through the amniotic fluid.
#5: Posterior baby back pain
When the baby’s head enters the pelvis in the posterior position and labor starts, the main symptom the woman usually feels is pain in her back. This is commonly known as back or posterior labor.
When babies are in an OA position, the contractions apply pressure to the occiput, towards the front and on the cervix and the vagina.
In a posterior labor, the occiput is towards the mother’s sacrum. When the uterus contracts, the pressure is directly applied to the bony back part of the woman’s pelvis.
This causes intense back discomfort, which increases as labor advances and disappears the moment the baby’s head rotation occurs.
Mothers in labor with posterior babies tend to request hard, constant pressure on the sacrum during each contraction while the baby is in an OP position.
Why does the baby adopt an occiput posterior (OP) position?
Most human beings will try to find the position in which they feel more comfortable. Babies in utero are no different.
During pregnancy, babies consider the uterus as a hammock and they will place their backs on it. Imagine lying on a hammock on your front. That’s definitely not very comfortable.
For the baby to adopt an OA position the mother’s front needs to be comfortable to lean against. This means the mother’s main positions must be forward-leaning ones.
When a pregnant woman sits down for long periods (at a desk or in a car) or leans back, as she reclines with her feet up after a long day, the baby will feel most comfortable lying on his mother’s back.
Think of how women live their lives in developing countries. The maternal positioning they adopt is mainly to take forward-leaning positions – like those we used to adopt not so long ago.
Before labor begins, take some time to note your posture and work to correct it, so as to encourage baby into an OA position.
Posterior birth complications
We’ve discussed the increased pain a pregnant woman experiences during labor due to this malposition. It often means women ask for stronger pain relief – often in the form of epidurals.
Epidurals can relieve back labor pain but they don’t allow for mobility. This means the mother is lying down while in labor, and there is nothing to encourage the baby to rotate.
If the baby can’t be born in an OP position, he might extend his neck (instead of tucking in his chin) and the posterior presentation ends up being a face presentation.
Depending on how deep in the birth canal the baby’s head is, a decision to make an emergency c-section might be made, as the pressure exerted on the baby’s face will be quite heavy.
OP babies who end up with a face presentation will have a sore, bruised face for a few days after birth.
If the baby continues with a tucked head, the second stage of labor will take longer and the baby might have a swelling, called a caput, after birth.
Tearing of the perineum is another of the risk factors more likely to occur if a baby is born in the occiput posterior position.
The chances of the baby needing help to be born – either by forceps or vacuum, or via a c-section – are much higher if he presents in the OP position.
We all know how much extra care and recovery time a mother and a baby require when interventions are needed during birth.
Posterior baby c-section rate
Research done in this area shows babies in the posterior occiput position during the second stage of labor are at a higher risk of being born by forceps or c-section.
However, researchers are cautious about the number of variables in their studies (occiput posterior, transverse positioning, stage, size, mobility, epidural usage) and agree that a well-designed randomized controlled trial is necessary to clarify these findings.
How to turn a posterior baby
After everything we’ve just learned about posterior babies, I’m sure you agree the best action is to try to avoid babies entering the pelvis in the posterior position.
As in most cases related to our health, prevention is key.
The number one rule to avoid posterior babies: during pregnancy – especially in the last few weeks – adopt positions where your hips are higher than your knees as much as possible.
Also try to make sure the baby leans on your belly and not your back, to achieve optimal fetal positioning. Avoid slouching on a sofa. If you do lie down, lie on your side.
If you’re sitting on a chair, sit upright and make sure you lean forward. Some women turn the chair so the backrest is in front of them.
If you have to spend a long time sitting on a chair, replace the chair with a birth ball. You can also use a kneeling chair.
Sit on a cushion, to bring your hips higher when you sit in low seats, such as in a car. Make sure you are safe, with your seat belt positioned properly across your lap and chest.
Don’t worry if your baby isn’t in the optimal head-down position (occiput anterior) when labor starts. Rotation of the baby’s head is most likely to happen, especially if you follow the signs your baby and your body send you.
Back labor happens for a reason. Mother nature is communicating what you must do.
During early labor, if your back hurts during contractions, you might want someone to put pressure on your sacrum for relief. This will mean you have to lean forward, which encourages baby to rotate forward too.
During posterior labor, most women will adopt forward-leaning positions – for example, on their hands and knees or standing and leaning on the wall, their partners or midwives.
Hands and knees positioning tends to be ideal during labor. Make sure you change position regularly and come back to the hands and knees posture as many times as you need to. Being on hands and knees is the ideal position for the fetal head to adopt the anterior position when it makes contact with the pelvic floor.
Avoid labor pain relief (like heavy epidural analgesia) that will completely prevent you from being mobile and active, upright, and leaning forward.
Water immersion, a TENs machine, acupressure, and Entonox are the best methods of pain relief to help you stay in the right position for the baby to achieve anterior rotation.
Acupressure is a variant of traditional Chinese medicine (TCM) where, instead of inserting needles, pressure is applied to acupuncture points.
The acupressure point to help turn a posterior baby during labor is called Urinary bladder 60.
Your partner, midwife, or doula can apply pressure on the point, with the thumbs, between contractions. My personal experience using this point on women during posterior labor has shown amazing results.
There are other useful techniques, such as the double hip squeeze that can give baby more room to achieve rotation during labor.
Mother Nature knows best and will guide mother and baby to work together to achieve an optimal outcome for birthing, even when the baby is in a persistent occiput posterior position.
If you follow this advice, your chances of having a posterior baby are very slim. You have plenty of tools to work with if you have an OP baby when you go into labor.