Tuesday, April 28, 2009

Belly Shape and Fetal Position

We've discussed briefly before that belly shape can tell you a lot about the position of your baby before birth.

Now let's get into specifics about fetal position, how it can influence labor and birth, and why it is so relevant for women of size in particular.

Anterior vs. Posterior

The classic big round "basketball belly" usually means that the baby is anterior. The back of the baby's head ("occiput") is towards the mom's front (which is why the position is called Occiput Anterior or OA), and the baby's eyes are looking towards the mama's back.

Look at the picture below and notice that the mother's belly looks big and well-rounded. This is because it is following the curve of the baby's back (and later, when the baby's head engages, its bottom).

Generally speaking, occiput anterior is the ideal position for birth. As long as the baby's head is lined up well, there are no arms/hands in the way, and it tucks its chin, chances are that the birth of an anterior baby will progress smoothly, especially if labor is allowed to start spontaneously.

Obviously there are exceptions, but research supports that anterior babies have more normal, uncomplicated labors and vaginal births than other positions.




Anterior
Baby
Belly







A lumpy, bumpy, not very noticeable belly (especially one with a curved-in spot around or near your belly button) often means that the baby is posterior. Look at the picture below and notice how the belly is not as rounded and has a "dip" below the belly button.

In this position, the back of the baby's head (occiput) is towards the mother's back, so the position is called Occiput Posterior or OP, but most people think of it as the baby facing up, towards mama's belly ("stargazing").

This is usually a much harder position for birth because the diameter of the baby's head in OP is larger and doesn't slip through as easily, and because pressure on the cervix tends to be uneven and so labor progresses more slowly.



Posterior
Baby
Belly

(baby
facing
slightly
to the
side)



Go back and compare the two pictures above again. Notice again the difference in the shape of the mother's belly. The anterior baby belly is more rounded, while the posterior baby belly is more lumpy and bumpy and has a concave area just below the belly button.

Other Differences Between Anterior And Posterior

There are other differences between an anterior and posterior baby too. These include where the mother feels the baby's movements most strongly, how "pregnant" she looks, and clinical signs such as where the fetal heartbeats are found, etc.

Movement

With a posterior baby, often the mom feels lots of weird, fluttery movements in front (the baby's hands and feet). Mom usually feels a lot of movement, pretty consistently, and feels it quite strongly.

With an anterior baby, most movement is usually felt in the upper right-hand quadrant of the belly (or upper left-hand quadrant sometimes), and while she certainly feels her baby's kicks and movements, the feeling may not be as strong or as constant as with a posterior baby.

Belly "Look"

With a posterior baby, people often comment the mom doesn't "look" very pregnant. The belly is not as rounded and doesn't stick out nearly as much.

With an anterior baby, the mom looks much more pregnant. She usually has a more rounded "basketball" belly, and it sticks out amazingly far, like she is ready to go into labor at any minute.

The mother can have the same size baby but look totally different day to day if baby shifts position, and will look a lot less pregnant when baby is posterior than when baby is anterior.

Fetal Heart Tones

Clinically, there are a few other signs as well. With a posterior baby, fetal heart tones are usually more difficult to locate because the baby's back is away from the front of mom's belly. Clinicians usually have to search for the heart tones for a while before they find them and the tones may appear and disappear with even small shifts in the baby's position.

With an anterior baby, fetal heart tones are more easily located because the baby's back is up against the mom's belly. Heart tones are most typically found in the lower left-hand belly area, and they usually stay audible pretty well, even as the baby shifts a bit.

Caveats

Now, please note....fetal position is not that important until near term. Babies need to exercise like anyone else, and they will flip and turn and rotate and surf all through pregnancy until near term when they get too big to do so much gyrating. So before close to term, fetal position is not really something to be all that concerned about. Babies flip around a lot and it's no big deal.

However, if near term (getting near 37+ weeks), you consistently don't "look" pregnant, you tend to feel baby's movement all up front, you tend to have a concave belly around the belly button, and your birth attendant consistently has a difficult time finding the baby's heartbeat (and doesn't usually find it on the lower left-hand side of your belly).....you may have a persistently posterior baby.

If so, it may behoove you to see if you can influence your baby's position before labor. More on that later.

Why Fetal Position is Relevant

Although babies do shift their positions a lot in pregnancy and labor and it's important not to obsess too much about fetal position, a baby that consistently stays in a posterior position can be a cause for concern.

Labor with a persistently posterior baby tends to be longer, harder, and more painful than with an anterior, well-aligned baby. Furthermore, because posterior labors tend to be longer and more painful, they often have more interventions associated with them (breaking the waters, artificially strengthening contractions with pitocin, epidurals for the pain, more vacuum extractions, etc.), and babies may experience fetal distress more often.

As a result, most research shows that the rate of cesareans associated with persistent posterior babies is much higher than the rate associated with anterior babies. In one 2006 study, researchers found that a persistent posterior position was associated with 13 times the risk for cesarean section.

Thus a persistent posterior fetal position can be a cause for concern late in pregnancy, and awareness of fetal position may be important.

Fetal Position and "Obesity"

Fetal position is particularly relevant to women of size. Although no one has studied the issue of fetal position in "obese" women really conclusively, some recent research does show a higher rate of persistent posterior babies in "obese" women. (More details on that later.)

Older research (from the 50s, 60s, and 70s, when they paid more attention to fetal position), also sometimes noted a higher rate of malpositions (especially posterior) in "obese" women.

Anecdotally, my own birth stories and the birth stories of many fat women I've received over the years for my website seems to support the idea of a higher rate of malpositions as well. This may be one reason (among many) why our cesarean rate is higher (especially for "CPD" or babies that don't "fit" well).

More on how fetal position affects labor in the next post, and later, what you can do to try and encourage good fetal position before and during labor.

18 comments:

Jen said...

This was a really informative post and clarified something for me I'd been wondering about. I'm pretty sure my son was persistantly posterior and I ended up with a 22 hour, extremely painful labour that ended in a c-section. We also did morphine for pain and pitocin to speed things up (but it sure didnt' work!).

Piffle said...

My eldest was posterior, or as we called it "sunnyside up". He was also big, 10lb, 9oz. My labor was long and I ended up with a C, he'd gotten stuck at position 0 and just wouldn't budgefrom there. We tried pitocin for about twelve hours I think. Just couldn't get him out. I wish I'd known this data back then; I was always getting comments that I couldn't be that far along; and we always attributed it to my wide hips. Plus I had a consistent pain just under my left lower ribs, like a bruise almost.

MJK said...

Yes, thank you for this post. It had never occurred to me that there could be that much difference based on how the baby was positioned. And the kick patterns too! I'm not very good at "name that bump" yet, and it means I don't have to wait for my midwives to point stuff out to me at the next appointment.

Evan and Clover and Co. said...

My first baby was posterior until I got to the first birth center. It was all back pain--nothing to do with my belly. I had been in labor for close to 20 hours (not too bad, thankfully), but once I felt her slip, and felt the first belly contraction, it went quickly!

Amoret said...

Thank you for this post--it explains so much about my third trimester and my daughter's birth. I knew that she was facing the "wrong" way, but I attributed my s-l-o-w labor and subsequent interventions to __________ (fill in the blank with whatever fat-negative thing you can think of). My water broke on a Tuesday morning, but she wasn't born until Thursday because my labor wouldn't progress, even with the Pitocin. (I had nurse-midwives and lots of monitoring, or else I surely would have had a C.)

I love your site and share it with all of the well-rounded mamas I know.

vbacwarrior said...

I have a question. My belly generally fits the anterior position description, except that the part of my belly that sticks out most is the lower part, not the upper part as in the picture that was shown. Thoughts?

Anonymous said...

So cool to see this in pictures! Now I think that my daughter may have been posterior, until I went into labor. I carried like I had swallowed a "wedge pillow" and occasionally could see her feet pushing up on my belly. However, when my water broke before labor began, I ran to the bathroom to sit on the toilet until the deluge stopped. As I sat, I could feel her wiggle and turn herself around, and she was born anterior, easily. However, I never thought about her being posterior prior to my water breaking. I have had 2 surgeries thru my belly button, and have alot of scar tissue in my abdomen around my belly button. I wonder if this kept her in a posterior position until my water broke? What do you think?

Milk Mama said...

My daughter was posterior. Looking at that photo, I said, "Oooh!" My belly looked just like that and I never looked as far along as I actually was until the latter weeks (35+). And yes, it was a difficult birth was back pain and a vacuum.

Stacey said...

This post is great!! At 33 weeks it sounds like my baby is a classic example of being in a posterior position. I've been asking my doctor about it and she just joked about my practically non existing bump and told me not to worry until I was at 37 weeks. It's nice to have a little insight on what's possibly going on!

Anonymous said...

Yes, Omg I totally agree; this is an AWESOME article, thank you!!!! My 1st preg., I was ALL stomach n remember feeling my daughter move all around. I am now 22.5 weeks n have only been feeling movement on my left n very low in pelvis PLUS what little belly I have, I noticed looks like the one with a 'dip' AND I too get crazy looks that I don't look pregnant at all. Glad to know y, but I won't complain lol1

the notorious b said...

My son was turned the wrong way and the nurses had me rock for an hour or two (I think - time was a mystery during labor) and he turned! Awesome trick!

Anonymous said...

I'm 30 weeks and my latest report showed my baby is in a posterior position. I'm so worried. I don't want to have a difficult labour

Well-Rounded Mama said...

You still have lots of time for that baby to turn; I wouldn't get too upset about it yet. Babies move around a lot near the end of pregnancy. They'll switch many times between now and the end of pregnancy.

That said, there are a number of things you can do to encourage a posterior baby to turn anterior as you get nearer to term. Seeing a good pregnancy chiropractor (who knows the Webster Technique) was key for me personally. If you are really anxious you might want to consider that possibility.

I have a whole list of ideas on my main website, www.plus-size-pregnancy.org, in the Malpositions FAQs there. It's also good to be sure your provider is trained in the technique to manually turn a posterior baby during labor, which has shown GREAT results in a number of recent studies.

Don't panic at this point, because it's early still, but if you'd like to be proactive, start seeing a pregnancy chiropractor and spending time on hands/knees. Then also read up about other techniques on my website. Best wishes to you!

Rae said...

What a well thought out, nicely worded article until the wording of the very last paragraph. Which cheapens and discredits the entire article. ("...of many fat women I've...)

Well-Rounded Mama said...

Rae, obviously you haven't read my site very closely if that bothers you. Look at the section in the menu above titled "Terminology" for more explanation.

It discusses the debate over what words to use to describe weight and size ("obese" or "fat" or "overweight" or all the various euphemism alternatives) and why I choose the words I do. I do so with great thought and care.

"Fat" is not a bad word or a judgment, it's simply a description of size. I'm sorry you can't yet hear it as such. Read more information about it before you dismiss such usage out of hand. Even if it's not the term you would choose, hopefully you'll understand why some of us do choose it. And then maybe hearing it won't make you automatically discredit everything that's gone before it.

Haraslou said...

I am certainly NOT fat, am 39W, 5 days and have an OP positioned baby... I am still exercising daily and in fact have lost weight in the last week or so.... (of the small amount I have put on during my pregnancy). Unsure how accurate comments regarding larger ladies having a predisposition for OP positioned babies is?? I have a lot of movement daily and I am hoping she will roll back the right way when the time comes... Good luck everyone out there!

Well-Rounded Mama said...

Haraslou, there is some suggestion in research that larger women may have a higher rate of OP babies, but that research needs to be confirmed by other research (which no one is doing at this point). But many larger women do NOT have OP babies, and many smaller women DO. There's certainly not a 1:1 correlation.

Most babies will rotate to OA during labor....but not all will, and those tend to be longer, harder labors. It helps to have a provider who knows how to manually turn an OP baby, as this really improves vaginal birth rates.

If not, a good pregnancy chiropractor can help align the pelvis, which helps many cases of OP babies rotate OA.

Shaunacey said...

What an informative article! You answered so many of my questions I have been wondering about for months now. This is my 4th pregnancy and right from the start of feeling movements I knew there was something different than the others. All my other babies had been anterior. But with this one, who also has the placenta on the posterior side, I could feel so much more movements all over the front the last few months. I am 37 weeks now and baby is mostly posterior. It has turned sideways a few times too. It still moves alot though, so I am not too worried. I am also showing smaller and my babies have been in the 8lb 6oz to 10lb 4oz range. So I was starting to wonder if this baby is in fact smaller, when my gut tells me the baby is big like the others. I am planning another homebirth, so it would be nice if this baby turned anterior for labour.