A baby is posterior when the back of his/her head is toward the mother’s spine. In my work as a doula I've noticed that posterior babies tend to give their mamas a lot of trouble. I've had clients report that their doctors seem ambivalent when a baby is posterior. I get it - babies move and posterior babies can still be born vaginally, but these births can be HARD for the mom. Really hard. And because there are some simple things that you can do throughout your pregnancy to help achieve a more ideal position, it seems naive to let chance dictate. This post is not about how to turn a posterior baby. Gail at Spinning Babies has wonderful resources for determining if the baby is posterior and then helping turn the baby. There is no need to reinvent the wheel. I would, however, like to take a minute to talk about why every pregnant woman should care about her baby's position and the few simple things she can do to help baby rest in the ideal position.
This main problem with a posterior position is that it makes it more difficult for a baby to tuck its chin. If the baby can’t tuck its chin the top of the head (as opposed to the crown) is the first part of the baby’s body to come through the pelvis and birth canal. This is important because the crown of the baby’s head is smaller and the bones are not fused so they can squeeze together to come through. The top of the baby’s head is a larger surface area and does not mold, so this baby will have a much more difficult time fitting through the mother’s pelvis. This position can have a variety of effects on a birth and sometimes none at all, but most often a woman with a posterior baby will experience one or more of these symptoms:
Water breaks before labor starts When a baby is posterior it is more likely that the bag of water will rupture before contractions begin. Most often doctors would like the baby to be born within roughly 24 hours and will take measures to augment labor. If labor does not become active within 6-12 hours (depending on the doctor) your care provider is likely to recommend induction with pitocin.
False labor As the body tries to turn the baby into an optimal position, a woman may experience false labor. Often waves will start in the evening and may die down by morning. This can happen over several days, leaving the mom exhausted and frustrated by the time labor starts. This process is called prodromal labor. Truthfully, this is one of the hardest aspects of laboring with a posterior baby. So much of a woman's energy is sapped before labor even starts! In my opinion this is the main reason so many women with posterior babies end up with an epidural.
Delayed Birth Process and Irregular Contraction Pattern Because the baby is in a more difficult position to fit through the birth canal, it will often take more time. The uterus contracts as it attempts to turn the baby into the optimal position, resulting in intense contractions that do not coincide with cervical dilation. It can be confusing for the parents as waves come regularly and with intensity, but they do not have a typical labor pattern - sometimes frequent but short contractions, sometimes long, but infrequent contractions. Additionally, labor may plateau and stay at a certain number of centimeters dilation for several hours. In this scenario, pitocin augmentation is often recommended by a care provider and it is not unusual for a women to request an epidural as a result of exhaustion and discouragement.
Back Labor Often women who have a posterior baby will complain of back labor. This is because the hardest part of the baby’s head is pressing on the back of the pelvis, and the fit is generally tighter which causes more pressure of the lower back. Back labor is in addition to the other normal sensations of childbirth.
Early Urge to Push In the posterior position the back of the baby’s head can trigger the Ferguson Reflex (the urge to push) early, so that a woman will feel the urge to bear down prior to complete dilation. This can be extremely difficult for the mother because (most often) she will not be allowed to push until she is completely dilated for fear of tearing the cervix.
Increase in use of vacuum A baby that is anterior is usually entering the birth canal with the crown of his/her head, while a baby that is posterior comes with the very top of his head. The crown molds more easily and requires less space to come through, while the top of the head is wider and inflexible. The posterior baby requires more effort to push the baby down the birth canal. Often there is an extended pushing time and the doctor may suggest the use of vacuum if the mother has been pushing more than two hours and having difficulty making progress.
Tearing when baby crowns When the top of the baby’s head comes first it will more likely cause tearing as it makes it’s way through the birth canal and perineum because it is a larger area and does not mold as well.
Increase in c-section Most often, when a c-section occurs with a posterior baby, it is not because the baby cannot fit, but because either the baby is experiencing distress or because there is no progress being made (either dilation or decent of the baby during pushing) and the doctor is not willing to give the baby more time or the mother is too exhausted to keep going.
How to tell if your baby is posterior With (Belly Mapping) you can use the baby’s movements to determine the baby's position. I think this is something really cool to pay attention to in pregnancy. Even if you don't do the drawing, taking the time to think about the movements you are feeling and what they could mean is a nice little bonding moment with the baby. I enjoyed visualizing my baby's little movements after I had belly mapped and was aware about his/her position. If you aren't into belly mapping or can't quite tell you can ask your midwife, who should be able to tell or you can ask about the position when/if your care provider does an ultrasound.
How to prevent/rotate a posterior baby The bottom line, here, is that the back of the baby's head is the heaviest part of the body. This means if you spend a lot of time reclining towards your back, you're encouraging the baby's head to rotate posterior. Think gravity, ladies! And forward postures! Be mindful to keep your knees below the hips when sitting, and even better sit Indian style. If you want to relax on the sofa, lay on your side instead of leaning back. Pelvic Tilts are also a great way to stretch your back and help the baby find the anterior position. Sleep is another opportunity to let gravity help pull the baby into an anterior position. I know it sounds uncomfortable, but using pillows (lots of pillows) to modify the Sims Position is the best sleeping position for pregnancy. I know it's so hard to get comfortable these days, but do your best. Gail has so many good things to say, I thought I'd share one more link to her site for further reading: Balance, Gravity and Movement.
As a note, there are other possible positional difficulties that would present with many of the same problems as a posterior baby. The preventative measures listed in this post would not have direct effect on the alternate malpositions.