Monday, December 6, 2010

The Fat Vagina Theory: "Soft Tissue Dystocia"

One common misconception that many birth attendants have about labor in women of size is the "fat vagina" theory.

In this theory, birth attendants believe that women of size have a lot of extra fat tissue internally, crowding the maternal pelvis and birth canal.  Extra fat tissue then supposedly gets in the way and obstructs the passage of the baby through the bony pelvis and/or vagina.

In medical research they call this "soft tissue dystocia," but sometimes doctors will patronizingly explain it to patients as the "fat vagina" theory.

[Note: "Fat Vagina" is an actual term used by an OB to tell a friend of mine from ICAN why she had a cesarean ─ she was told her morbid obesity made her vagina "too fat" to let the baby out during labor ─ and she's not the only one who has been told that.  So although my sarcasm meter is certainly on when I use it, that's really a term that has been used with some women of size.]

Alas, it's not just doctors who buy into the "fat vagina" theory.  One TV birth show featuring a midwifery practice even promoted this same theory, encouraging a fat woman who wanted a Vaginal Birth After Cesarean (VBAC) at their birthing center to lose weight during pregnancy in order to "decrease the fat deposits in the vagina" and "make it possible" for the woman to have a VBAC. (As if no fat woman has ever had a VBAC without losing weight!  Sorry, they have. And so have I.)

Or there's the story one of my blog's readers emailed to me:
[The midwife] said I will have a large fat buildup around my birth canal and uterus so baby will get stuck in a natural birth. 
Alas, this "fat vagina" belief is a theory near and dear to many birth attendants' hearts.  They have been taught in medical or midwifery school that "soft tissue dystocia" is the cause of many cesareans in fat women, and they believe it with all of their hearts.  It's very difficult to get them to question its existence. 

But what does the evidence say? 

The Research, Such As It Is

One of the most frustrating aspects of the whole "fat vagina" theory is how little actual evidence there is on it, yet it is taught as if it is clearly established science. 

One study (Crane 1997) describes it as a possible reason for a higher primary cesarean rate in "obese" women:
Perhaps dystocia due to an increased deposition of soft tissues in the maternal pelvis may lead to the observed increase in the cesarean delivery rate.
One review (Vahratian 2005) noted that many studies attribute the increased rate of cesareans in "obese" women to soft tissue dystocia but that few prove it.
Several authors have speculated that this association [between obesity and cesarean rates] may be due to the added soft-tissue deposits in the pelvis of obese women, which coupled with a larger fetus might necessitate more time and stronger contractions to progress through labor.  However, direct evidence of fat deposition in the pelvis is needed to support this assertion.
The study noted that as yet, the authors promoting this theory have failed to provide this evidence.

Most studies discuss increased maternal fat deposits as if it is a proven concept, but no one has actually done much study showing a real difference in maternal fat compartments, let alone proven that it affects labor.

Barau et al., 2006, also favors the concept of soft tissue dystocia but acknowledges that:
There is no direct support of this concept by medical imagery studies.
So why are healthcare providers so devoted to this theory when there is very little actual proof of it? 

Most of the time, practitioners believe in the concept of soft tissue dystocia because they know that visceral fat can build up around internal abdominal organs, so they speculate that a similar thing must be happening in the maternal pelvis.

Furthermore, they often observe more tissue during pap smears in "morbidly obese" women, sometimes needing to use a larger speculum in order to hold open the vaginal vault and do the exam.  Therefore, they jump to the conclusion that there is more fat "crowding" the pelvis of women of size, and that therefore, this must be obstructing the passage of the baby through the mother's pelvis.

But just because a fat woman's vagina tends to have more tissue to hold back with a speculum does not necessarily mean that there is enough fat way up inside the pelvis (pelvic inlet) or at the pelvic outlet to be clinically significant.  

Remember, because the considerable weight of a fat woman's abdomen presses down with the weight of gravity, it may tend to make the vaginal walls more prone to collapse and look overly crowded, but it may not actually be so, or not enough to make much difference. And even if there was somewhat more tissue in a fat woman's vaginal area, remember......fat squishes.  It's unlikely that there would be enough tissue there to actually impede a baby's exit, even in very fat women. 

The one study we do have that actually did medical imagery to discover whether there are extra maternal fat deposits in the pelvis does not support the idea that there is enough extra soft tissue to be relevant to birth.

Wischnik (1992) did a study on the "fatty pelvis" to see whether fat compartments within the pelvis actually resulted in "functional reduction of the birth channel diameters."  They found slightly more fat compartments, but did not find it to be clinically relevant.  They concluded:
The common assumption can no longer be maintained, that adiposity necessarily causes soft tissue dystokia  [sic] due to larger fat compartments within the small pelvis.
So from a strictly evidence-based point of view, there is no substantiated medical evidence of enough increased deposits to be medically significant. 

All we have is the observation that there is slightly more tissue pushing in and thus more need for a stronger speculum during the pap smears of women of size. 

I think most medical providers then take a leap of logic and conclude that if fat women's babies don't come out as easily as skinny women's babies, it must be due to fat blocking the way....and the need for a bigger speculum during a GYN exam in some women of size just seems to confirm that bias. 

But I think they need to look more closely at this assumption.

Alternative Explanations

Unfortunately, despite a glaring lack of evidence, soft tissue dystocia is a concept that continues to be taught and widely believed. 

Barau 2006 argued that although there is no hard proof of soft tissue dystocia, it must exist because there is an increase in cesareans due to prolonged labor in obese women compared to average-sized women with similarly-sized babies. 

However, I will point out again that a higher rate of malpositioned babies among women of size could also explain their longer labors and increased rate of cesareans due to labor dystocia.

Babies who face their mothers' tummies (occiput posterior) don't fit as easily through the pelvis, present with a larger head diameter, and often experience long, slow, hard labors.  Research clearly shows that posterior babies have longer and slower labors and have a much higher cesarean rate than anterior babies. 

Although the subject needs further study, some research has found a higher rate of malpositioned babies in "obese" women, and very old obstetric research also often notes in passing a higher rate of occiput posterior and other malpositions in women of size as well.

And anecdotally, women of size often do seem to have more malpositions, especially occiput posterior, many of which result in cesareans.

Many of these fat women have been told they had cesareans because of their "fat vagina" or "too small" pelvis.  Yet if you read their stories carefully, they had all the signs and symptoms of a malpositioned baby instead. 

Furthermore, many women who had cesareans for "fat vaginas" went on to have subsequent vaginal births with babies that were even larger than their cesarean babies....without losing weight first. This would be impossible if the problem really were a "fat vagina." 

The key was having a well-positioned baby, not losing weight or reducing maternal pelvic fat deposits. 

Another problem with the concept of the "fat vagina" is the inconsistency with which this diagnosis is applied. If a ~275 lb. woman (like my friend from ICAN) is told that her vagina is "too fat" and prevented her baby from getting out, then it follows that a 350 lb. woman should not be able to birth a similarly-sized baby vaginally. Yet we know that women of that size can and do have vaginal births. I have birth stories on my website of vaginal births to women at 300, 350, and 400 lbs.  Yes, women of this size have a high cesarean rate because they are almost never given a real chance to actually have a vaginal birth.....but it can happen when they are given a realistic chance.

If fat vaginas truly prevented vaginal birth as much as some providers think they do, there would be NO vaginal birthers above a certain size. Sure, vaginal birth is always a combo of factors, including pelvic size/shape, the baby's size and position, (passenger, powers, position, etc.), so some variability in who gives birth vaginally is logical, but if soft tissue dystocia were a really significant factor, really supersized women would never birth vaginally.  Yet many can and do, if they have a well-positioned baby and are given a realistic chance.

In my opinion, the real issue behind a higher rate of "dystocia" cesareans in women of size is probably fetal position, not fat vaginas. 

However, because doctors are trained to blame obesity as the go-to diagnosis when they don't have another explanation, soft tissue dystocia gets blamed for "blocking" the baby's way out. 

But that's just lazy thinking, not actual proof of soft tissue dystocia.

What About Shoulder Dystocia?

Another fear that many doctors and midwives have is that extra soft tissue in a fat woman's vagina might cause such a tight fit for the baby that the baby's shoulders will get stuck ("shoulder dystocia"), which can be a true obstetric emergency.

This fear seems borne out by studies which have shown higher rates of shoulder dystocia in "obese" women. Yet many of these studies did not control for other factors, like macrosomia, diabetes, forceps/vacuum extractor, or induction, all of which increase the risk for shoulder dystocia, and most of which occur at higher rates in women of size. 

It's important to note that other studies have found that obesity is not a risk factor for shoulder dystocia when these other factors are controlled for. 

Furthermore, it is not extra fat crowding the vaginal walls that causes shoulder dystocia. Rather, shoulder dystocia is caused by obstruction by the bony pelvis, not soft tissues. A complex interplay of factors results in shoulder dystocia, including fetal position, maternal position and mobility, pelvic shape, induction, operative delivery, diabetes, and macrosomia. 

But justified or not, fear that "extra" soft tissue will cause shoulder dystocia is a big contributor to the high planned cesarean rate and early induction rate in women of size. 

But What If Soft Tissue Dystocia is Real?

Frankly, soft tissue dystocia as a concept has not been proven at all, but some care providers believe in it with all their heart and refuse to be dissuaded from the possibility, pointing out that it hasn't been disproven conclusively either.  That's a fair point.

To these providers I would argue that IF soft tissue dystocia were indeed real, then it is vital to change how most providers manage the labors of women of size in order to minimize its theoretical impact.

The typical way the labors of many "obese" women is managed often includes inducing early, breaking the bag of waters early, strongly encouraging early placement of an epidural "just in case," strictly limiting mobility, and using semi-sitting or lying back positions for pushing. Yet these measures often limit the amount of pelvic space the baby has to fit through.

If a bunch of extra fat is supposedly crowding things already, these restrictive protocols just make things worse.

IF soft tissue dystocia were real, mobility in labor would be even more important to women of size because it opens up the pelvic dimensions and gives "obese" women the best possible chance to help that baby fit through. Yet "obese" women have the most restrictions on their mobility in labor and are the least encouraged to try alternative positions for birth.

If a provider truly believes that soft tissue dystocia might be real, then the answer is not to pre-emptively induce or section women of size, but to give them every chance at creating more space in the pelvis. 

This means not having her in the usual lying back/semi-sitting position, which puts pressure on the tailbone and presses it into the pelvic cavity, reducing the space available. 

This means not requiring/pressuring her for an early epidural (as many practices encourage with women of size), so that she can move freely during labor and encourage her baby to be in a good position for birth. 

It means not breaking her waters early in labor, so the baby has the watery cushion to help it move into an optimal position. 

It means letting her stay upright as much as possible, so she can use gravity to help bring that baby down and press it through those supposedly fat-crowded walls. 

It means letting her push in whatever position feels comfortable to her, encouraging her to stay mobile, and letting her utilize things that will help her stay mobile more easily (a labor tub, a dangling support or trapeze bar, a squat bar, etc.).

Personally, I don't believe that soft tissue dystocia is clinically relevant, but if you are a provider and you firmly believe in its existence, follow that to its logical conclusion and utilize labor protocols that help that woman maximize her pelvic space, not inhibit it via restrictive protocols. 


Soft tissue dystocia is a belief that is near and dear to many doctors' hearts (and sadly, even to some midwives' hearts). Yet despite no research to support it, it as taught as if it is fact. 

At this point, soft tissue dystocia is NOT fact.  It has not been proven at all, and remains highly speculative as a possible cause of labor issues.

Furthermore, many women of size who have had their cesareans blamed on "fat vaginas" have gone on to have vaginal births in later births----without having lost weight first.  If soft tissue dystocia were really the cause of their cesareans, this would not have been possible. The issue for them was fetal position, not maternal soft tissue. 

The "morbidly obese" friend of mine who was told that her "fat vagina" was the cause of her cesarean?  She has since gone on to have TWO vaginal the same maternal weight, with similarly-sized babies.  So much for her "fat vagina" preventing the baby from coming out! 

And then there's the commenter on my blog who had a similar experience: 
I was told by my OB, while on the operating table and again at my 6 week check, that 'my vagina was too fat to birth a baby naturally'. Had a VBAC 3 years later though!

[Comment on 10-12-10, on Prenatal Weight Gain: The Importance of Study Design.]
Far too often, "fat vagina" is just a convenient excuse for lazy thinking, a handy scapegoat for the high cesarean rate in women of size, and a convenient excuse for blocking access to VBAC in yet another group.

And unfortunately, it prevents caregivers from examining their own care practices and how iatrogenic influences like weight bias, induction, fear of macrosomia, restrictive protocols, "failure to wait" and fetal position issues are the real factors driving the cesarean rate for women of size.  


Anonymous said...

I am a single woman without kids, but I really appreciate your blog in case I ever do decide to have children. It kind of makes me dread dealing with the medical community, but also gives me hope of what can be.

Unknown said...

Interesting article. I have never been told that I have a fat vagina, but I can see how the medical world would view obese women's vaginas as fat, and find ways to manage labor towards a c-section.

The only concern I have about adipose tissue in obese pregnancy is the event of excessive tearing. When I had my daughter, I had such a severe event of tearing that it took 18 stitches to "fix" it, and it's still messed up four years later.

I'm sure the likelihood of severe tearing could be addressed with the use of gravity-assisted pushing, the end of purple pushing, and avoiding vaccuum and forcep extractions...ah well...

Anonymous said...

So if there is a higher incident of mal-positioned babies in large women, doesn't that make a case for large women who are about to get pregnant or are pregnant to want to do something? Maybe it's not completely "fat vagina" that results in c-sections but certainly the woman's size leads to the mal-position and that leads to a cs. I'm considered obese and I when I read a blog like this, I think, "gee, maybe I should do something to up my chance of a vaginal birth" instead of "how dare they call my vagina fat". We have to take responsibility for the situation we're in. Pretending that the medical community is against us isn't going to help us get better maternity care.

kelly said...

Thank you for a thorough article on what seems, to me, to be a theory unproven yet widely adopted by patriarchal, condescending, anti-woman, fatphobic people! Very interesting!

wriggles said...

The colloquial expression is;

"more cushin' for ya pushin'"

I think we'll find this is the deeply 'scientific' genus for this theory.

Heather said...

Wow, this is a very interesting and thorough article! I knew that women of size were more likely to have a c-section, but I've never heard this excuse. I've always heard "suspected macrosomia" as the culprit. Anyway, great article. Thank you for writing it!

Anonymous said...

I just have to say something. I am a midwife myself and I am appalled that a midwifery practice would EVER encourage ANY woman to lose weight while pregnant, no matter what size she is. That baby needs nourishment!!!!
I've never been concerned about an overweight woman's baby being able to come down the birth canal. Why on earth would I? This is absurd to think that fat causes a dystocia of the birth canal. I am not overweight, but that's not an excuse to treat an overweight woman like her feelings don't matter and no reason to think that her vagina isn't as important as mine. If practitioners treat heavier women like airline hangars when they get a pap smear, that's abuse. Overweight women have just as much nerve feeling in their vaginas as any other woman and they deserve respect when doing medical procedures. No wonder so many overweight women go years between pap smears, even if they have a history that calls for one. They shouldn't be afraid to go to the doctor/midwife to have normal health screenings!!!!! Midwives reading: If you use a latex condom over a NORMAL sized speculum, and cut the end off, the tissue will not crowd the exam, and your client will be much more comfortable. You can even use a pediatric size speculum this way on an obese woman. It's especially important if she's still a virgin or if she's been sexually mistreated in the past that you use the smallest speculum you have. But, even if she hasn't, her vagina is just as sensitive as yours!!!!! Be gentle!!!! (sorry, this just made me mad to think that there are health providers who think this way. All women deserve respect.....stepping off of the soap box now.)

Michelle A. said...

"One review (Vahratian 2005) noted that many studies attribute the increased rate of cesareans in "obese" women to soft tissue dystocia but that few prove it.

Several authors have speculated that this association [between obesity and cesarean rates] may be due to the added soft-tissue deposits in the pelvis of obese women, which coupled with a larger fetus might necessitate more time and stronger contractions to progress through labor. "

I'd like to see the data which supports the assertion that women who are obese pre-pregnancy have larger babies than non-obese women. Maybe the above means to say "in the event of a larger fetus" and I'm misinterpreting it?

Mostly I just figure if she wasn't too fat to get a baby IN then she won't be too fat to get a baby out. Sheesh. Can you imagine? I'm sorry, your vagina is too fat for sex!

Tanz said...

To the anonymous commenter who is also a midwife: sadly, I had a midwife during my last pregnancy - a twin pregnancy - tell me to not gain any weight during it, and offer to send me to a nutritionist in order to 'help' me achieve it. She also treated me from the very beginning as though I would inevitably end up with high BP, pregnancy diabetes and pre-eclampsia. I switched from her care to that of another, but I was shocked to find a midwife, of all people, with that approach.

Even sadder, though, is that when I (calmly) state why I do not recommend her to other mothers I am told that I was irresponsible to not take her advice, and that I should 'shut up' about my experience as it was just a 'matter of opinion' and she was 'doing her best for my health.'

To the other anonymous poster; Just because fat women have more c-sections than other women does not mean the fat itself is the cause. Until we find out what that cause actually *is* we will continue to have such high c-section rates amongst fat women.

Pounce said...

Can I print this off to give to my FORMER midwife please??? The same one who told me my vagina would be too fat to give birth normally, that I wouldn't be able to spread my legs wide enough to give birth normally because they're too fat and that both ultrasounds and fetal heartrate monitoring would be significantly impeded if not impossible because of the fat on my belly? (BTW at nearly 25wks, all ultrasounds have been perfectly normal with no problems getting images and equally my new midwife had no problem finding my baby's heartbeat even through that fat old tummy!)

Cassandra said...

To the anonymous person who said "We have to take responsibility for the situation we're in." Well, I did by going to Spinning Babies and being proactive about making sure my baby was in an OA position, the best position for birth. During my long beginning labor stage, my birth team believed the baby had flipped during a contraction and made me do an ultrasound (since it was a birth center and they can only deliver breech at home). Lo and behold, there she was, in perfect OA position. I weighed 400lbs pre-pregnancy and my mother had two OP babies leading to c-section and she weighed way, way less than me. So weight and genetics against me, the birth was totally uncomplicated.

Anonymous said...

I had a doctor tell me the fat vagina story before the birth of my first. Unfortunately, his practice is the only one in my network within feasible travel distance. So to be safe, I'll have to wait until I am absolutely positively beyond my childbearing years (I'm theoretically done, but still fertile) before I can tell him that I have never needed the help of an OB to have babies. Fat twat my fat ass.

Word verification: sparst. The evidence for a lot of things that are done to women and babies under the U.S. medical model is pretty damn sparst.

Anonymous said...

I have been carrying around emotional trauma and guilt about my 2 csections for so many years. I have always felt that my csections and failure at vbac were due to my obesity (I was almost 250 lbs at delivery); that it was my fault. You have given me a new perspective and perhaps a path to healing.

SPRING said...

As a LARGER woman I have never been told that my vagina was fat. My children were both large and I had NO PROBLEM pushing them out. I had one that was 9lb3oz and came out in 3 pushes. so I think this is just another excuse Drs are using to make more money by doing Cs.

Anonymous said...

Thank you for posting this. I had a c-section with my first baby seven years ago. I was "warned" by my OB that since I was so big, 330, and had more fatty tissue in my vagina that I could put my baby in jeopardy trying to deliver him naturally. She told me that i could break his collarbone, dislocate his shoulders or he could just get stuck. I went against my gut and allowed myself to be induced 3 weeks early. When my doctor came in to check on me after the first couple of hours, she broke my water with out my consent and the clock started ticking. After 24 hours of labor, I was so close and my doctor ordered me into an emergency c-section because my water had been broken for too long, putting my baby at risk. Adding insult to injury, I had not had any pain medicine (i'm kind of granola). The anesthesiologist came in to give me the epidural and took one look at me and said that it is really tricky to do on such a fluffy girl. I begged for her to try. She told me that she was going to give me some oxygen before she started and out me to sleep. I woke up so confused. And worst of all I feel I missed the birth of my son. He was very sick and had under developed spots on his lungs, he was taken away to the NICU immediately. I didn't get to hold him until he was 6 days old.
I really wish that I had trusted my instincts and had had a provider who listened. I am pregnant again I am prayerful that this time around I will be able to have a natural birth free from all of the bullying that I experienced before. I have to believe that my body big or not would not grow a baby that it could not deliver.

Jamie Parker said... can I just say: A) I love you! Thank you for being a fat-friendly advocate and educator for those of us with REAL bodies! And B) Thank you for bringing attention to yet another cop out on behalf of "big medicine" so they can take the easy way out!!!!

Marlenecpm said...

I do believe o'wt women are more likely to have a "fat vagina", however, I do not believe it is related to dystocia. But what does happen, is that the baby is very comfy on his nice soft fluffy "pillow" & can stay higher up (not engaged) much longer into labor than others. I was taught that if a skinny moms baby was still floating (not engaged) by active labor,there is a chance of CPD, but if a larger moms baby is still up there in active labor, just wait for it & it will eventually come down. Without this insight, a lot of unnecessary surgeries are performed. Please, if you want a natural birth, use an authentic, traditional midwife, not a doc or a medwife!

Rebecca is Fabulous said...

I realize this is an old post, but I cannot resist commenting. I am an overweight woman who has birthed three children naturally. My last was 8 lbs, 13 oz; I was in labor for eight hours, and pushed for less than ten minutes. I weighed 287 lbs. My second was 9 lbs, my first almost 8. Every baby was healthy, with lovely shaped heads. My recovery times were crazy quick, and I have never needed an episiotomy or stitches. My fat vagina kicks ass.

Up yours, unbelievers!

(and thanks for the lovely article!)

Catherine said...

Heard this excuse on a lot of the birthing TV shows too. I'm so thankful for your blog! I don't feel so alone in this battle for my right to birth my way.

Siv Klemets said...

Doctors are as prejudiced a group as any other, I think a key factor is how fit you are rather than absolute weight

Canada Business Directory said...
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Unknown said...

Yup, just got told this as a reason why I can't delivery my baby in a birthing tub. I'm with a midwife practice, but that doesn't seem to make a difference in how they treat women of size. If anyone's in the Minneapolis area, think twice before using the Minneapolis Midwives--they do actively discriminate against women of size (ordering extra unnecessary exams, preventing them from using the birthing tub or limiting its use, etc.). They seem like an excellent practice otherwise, but their stance on obesity is humiliating and unnecessary.

Anonymous said...

I don't know about yall. but I think I will be bringing a box of condoms to my next gyn exam. Thank you, anonymous midwife!

Anonymous said...

What a call to have to make.I can see lot of the troubles here with political views entering medicine. What a hard thing to prove, and at what price.I would suspect over weight has less to do with than genetics like how big are your body openings and how big is your mate compared to the woman.

Anonymous said...

I gave birth at around 350 pounds with an uncomplicated, un-induced labor that lasted about 19 hours from my very first contraction. My daughter had a double nuchal chord, which means the umbilical cord was wrapped around her neck twice, and that resulted in my having to labor lying on my back with an oxygen mask-- we tried different positions and that gave the best heart rate, in hindsight it must have prevented tugging on the cord. I had an epidural at about 6 cm after 15 hours of labor, and 4 hours later I only had to push once to deliver a healthy full term baby girl! If my vagina wasn't too fat, I doubt anyone's is.