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Myths of occiput posterior

   
There are some myths about laboring with a posterior baby.
Let's start with appreciation for Penny Simkin's brave confrontation of a dogmatic trend that has arisen over the last few years.  At first, I was rather surprised to hear a talk by Penny Simkin called, "The OP Fetus; How little we know." Now, the light has gone on. Parents and professionals alike have some misunderstandings about the influence of posterior presentation on labor. For instance, "She didn't have back labor so I didn't think the baby was posterior." Or, "We did everything we could because we tried hands and knees position in labor."

Sometimes a midwife or doctor will say they don't pay much attention to a head down baby's position in late pregnancy because some posterior babies come out fine. Emphasis mine. Spinning Babies is about the 15-30% that need more help than strong labor and the hands and knees position.

 



A 2005 study by Ellice Lieberman and her research group in Boston busted some of the myths that have been growing up around posterior labors (see a discussion about it on this web site). Unfortunately, people reading the study casually could also conclude that fetal position changes at random throughout the course of labor. Yet, in reading the data carefully we find several consistencies with previous research on the posterior fetal presentation and its effects on labor.

There is a difference in ROT/LOT starting positions brought to light by Jean Sutton in her Understanding and Teaching Optimal Foetal Positioning book. Observing this difference as well, I find that the lack of information on which transverse position the 48.9% (about half!) the babies started in makes the claim that fetal rotation has no rhyme or reason to be a little premature ideology. I also think that a good deal of the reason is in the mother's soft tissue tension, or in a significant lack of tension, and its effect on fetal rotation.

There is some truth and some myth in all this. So, I'd like to start with the myths of the OP position which Penny Simkin has helped us identify and then give my two cents worth-- and some of that I ask you to take on credit! I'll talk about bony and soft tissue contributors to whether or not a posterior baby may get stuck or delayed.

The Myths 

 

MYTH: It is important to know the fetal position.


You read it here first, folks. Yes, this is a Myth. No, it really wasn't said here first, I was just making a joke on myself. Midwives have been debating this, gently, for years. Penny Simkin brought it up this summer in her talk about What We Don't Know About the OP Baby.It is less important to know the fetal position than it is important to respond to the needs of the birth. The muscles, ligaments and bones may need acommodation regardless of fetal position. In other words, tension in the psoas pair of muscles or pelvic floor can delay an anterior baby and a posterior baby. Extension of the anterior fetus' head can prevent engagement in some pelvises. The main point is that we can, when needed, promote progress regardless of fetal position.

 
 

MYTH: If we prevent OP before labor than we can prevent OP in labor


To answer this question correctly we would have to study 2nd trimester prevention excersizes among one group of women with no prevention methods in another group. Why? Because while most babies that start labor in an OP position will rotate to OA before the end of labor, there is a consistent small group of babies who are OP throughout labor. This group are the mothers and babies that need Spinning Babies and Optimal Fetal Positioning. But how do we identify this group without helping the other mothers, too? And why wouldn't we help other mothers. We will. But because most OP babies rotate to OA , about 87% according to Gardberg, we shouldn't ignore the 15% (Lieberman) who are OP when they are born, either vaginally or cesarean.


 

OA MYTH: If the baby is Occiput Anterior (OA, the "best" starting position) in early labor the baby will stay in a good position throughout labor.


palpating a fetusThe recent Lieberman study confirmed statistical trends of earlier studies. 83% of the OA babies who were OA in early labor were OA when they came out. But a small 5.4% rotated to a direct Occiput Posterior position for birth.
 

 

 

 

Midwife Gail Tully palpates Reba's baby

 

 

 

 

 

 

MYTH: Midwives and Doctors can tell the baby's position.


Actually, sometimes we can and sometimes we can't. There are three common ways a baby's position is sought. By hands-on palpation, or feeling the abdomen. The bumps in the belly mean something to a practiced hand. THe problem is in the variation of bellys and bumps. Sometimes they don't make a picture that the person feeling can make out. Bellys come in different thicknesses. Babies sometimes are curled up in interesting ways. Lots of amniotic fluid or muscle strength can hide details that might be needed to "see" the position.

Feeling inside, through the open cervic sometimes gives clues. But the little sutures (not stitches, but lines showing where the skull bones meet) can be just out of reach or the edge of the soft spot (fontanel) can feel like a suture, oddly enough. Feeling babies position is not as simple as it looks in the books or on the plastic chart some hospital L & D units have.

Ultrasound can tell the baby's position. Funny we rely so wholeheartedly on technology. We are looking through dark water to see a 3-D person displayed on a 2-D computer screen. There can be blurred pictures of the crucial landmarks of the baby's head or the viewer can make a mistake.

Dr. Karen Davidson, the Ultrasound sonologist for the Lieberman group studying 1,766 women (see a discussion on this interesting study by clicking on a link below) in labor found she had to exclude 162 women because their ultrasound pictures were uninterpretable. In the first six-months of the study she found 13% of early labor ultrasounds were uniterpretable. She got really good at it as the study went on, but she was their expert to begin with, so I would think her early rates must be at least on par with the nation's Ultrasound interpreters.

Of the 1,562 births remaining in the Lieberman study 51% had an interpretable Ultrasound picture in late labor. That means 49% didn't. I don't think we can hang our hats on Ultrasound. And furthermore, how the baby's back is situated doesn't always tell us how the head is facing.


 

MYTH: Back pain is a sign of an Occiput Posterior (OP) baby.


Short women, women who aren't flexible, women who've had accidents, women who have weak back muscles and some of the women with posterior babies or babies who have one of their arms up in late labor. Some women in of each of these categories are likely to get some back pain in labor.

The women with OP babies in early labor (3 to 4 cm mostly) enrolling in the Lieberman study did not report more back pain at 3-4 cm dilation. Then as 92% of the women had epidural analgesia back pain was not investigated further in labor. As a doula of women with and without epidural pain relief, many without, I have noted that OP back pain, when it does come, often comes between 4 and 6 cm.

Some women have relatively straightforward OP labors, if we are still permitted to call labors by the fetal position name. These women often do not report back pain at an intensity to get attention. Some have no more labor pain in their backs as they do in the front. A few women have severe back pain early in labor, at 2 cm. These women are candidates for an inversion as soon as possible, if they will accept the task. Back pain is more about the fit of the baby than the position. Some posterior babies fit their mother's pelvises better than others. (See comfort measures in this section to find a few ideas for soothing back pain.)


 

MYTH: When a woman is having prolonged labor without back pain, it is from a reason other than posterior position.


Oh, thank you, Penny, for bringing this myth to our attention. I can't list the times a midwife, doula or nurse has told me their frustration at not being able to think of a labor progress trick to help a woman in long labor and then said something quite close to this, "I thought of the Open-Knee Chest position (or another technique) but didn't try it because she didn't have back pain. While the cesarean was being done, the doctor said the baby was posterior and that's why the baby wasn't coming through the pelvis."

A delay or a stall in labor, with or without back pain can often be corrected by one form of inversion or another. I write at length about inversion with tips to help it work better in the labor progress article in this section of the web site.

Back pain, with or without a stall in labor may also be soothed by inversion.

Sometimes back pain is from a spasm in a ligament low in the back of the uterus, such as the ligament holding the cervix to the sacrum. Inversion gives that ligament a gentle stretch and then when the mom gets up the ligament can relax. Ahhh.

There are some protective guidelines about inversion. See the article and ask your care provider if there is "a medical reason not to do it?" This great little question also comes to us via Penny Simkin, too.

 New research on a stall in the progress of dilation during the active phase of labor. California researcher Aaron Caughey found patience reduces cesareans by 1/3 (400,000 a year) in his study.

 

 

MYTH: Position changes can change the OP position in labor


This hasn't been studied like I'd like to study it. The studies aren't designed in a way that will answer anything but, 30 minutes of position changes are not enough to overcome the tension in the womb holding the baby in an unfavorable position.

These studies are why I developed the "3 Principles of Spinning Babies." First, you have to relax the involuntary muscles, including the muscle fibers mingled in the uterine ligaments. Second, you get gravity helping and third, move the pelvis in ways that open the level of the pelvis that the baby's head is resting at.

If the head is stuck at the brim, you don't open the bottom of the pelvis, for instance, and wonder why squatting works for some women and not for others. If your front doorbell rings do you open the back door and wonder where you company is at?

 

Pelvic shape and size does have an effect on the course of a posterior labor in a small percentage of women.

 

Four pelvic types with pubic arches for each

 four pelvic types

 

A pelvic shape which is longer front to back allows a few women to have a posterior baby without back labor, as long as there isn't another reason for back ache, like a muscle spasm.

A pelvic shape which is triangular, called an android pelvis, can make it hard for a larger, posterior baby to fit through. A woman with a smaller than average android pelvis will need to, in my observations, eat carefully to get good protein and vegetables without a lot of sweets and white bread. She will have to work on her babies position in the 2nd trimester, especially if she is a first time mom. That way she can avoid the scenario I have often seen of being 8 months pregnant and trying to get a large OP baby to turn around and get settled in the brim facing the back right SI joint.

The baby's back shifts right and left and right again trying to turn his little forehead out of the narrow pointy space at the mother's pubic bone. But the pelvis isn't round so he can't. He'll have to come up and out, away from the brim to turn. He can only do that if the mom relaxes her ligaments, and gets upside down a bit each day.

It isn't always comfortable, of course, to be 8 months pregnant and hang upside down for a minute. And even then, some of these moms need body work to overcome the muscle spasms in their round or broad ligaments. Hmm. Its much easier at 4 and 5 months pregnant. Even 6 months. If these few OP babies aren't able to navigate their mother's pelvic brim they will have to be born by cesarean. The problem is that few people, and I mean providers, can tell who will be the one that gets stuck and who will be the one to get through.

A woman with a round, gynecoid, pelvis has a much better chance of having her posterior baby rotate in labor. Depending on various factors, like eating in labor, keeping hydrated, leaning forward, being patient, resting belly down (somewhat) and avoiding positions on her back, having her water broke or an epidural that increases the likelihood of a challenge with the labor (length, vacuum or surgery) her baby may come around readily or only eventually. A long labor can soften up tight spots on the route out.



 

Pelvic shape isn't the only consideration, of course. The soft tissues are more often the case, especially when they aren't soft a bit!


 

Look in Real Stories to read, The Long Labor That Wasn't

 
 

References


The OP fetus; How little we know, Penny Simkin

Changes in Fetal Position During Labor and their Association with Epidural Analgesia, Ellice Lieberman et al.
Intrapartum sonography and persistent occiput posterior position: a study of 408 deliveries M Gardberg et al.

Human Labor and Birth, Oxorn and Foote

Holistic Midwifery, Vol II, Anne Frye

Labor Progress Handbook, Penny Simkin and Ruth Ancheta
 
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