Routine Cesareans Not Better for "Extreme Obesity"

If you are a "supersized" woman, many doctors won't even give you a chance anymore for a vaginal birth. 

They often argue that a cesarean delivery is better and safer in women with "extreme obesity."  They argue that it is unlikely that a woman that fat will be able to deliver vaginally, and even if they did, the baby is likely to be harmed via hypoxia or birth injuries. They also argue that if a cesarean during labor were needed emergently, doing one on someone of that size would lead to poorer outcomes because of the delay that could be encountered in getting to the baby. So many doctors contend that it's just better to plan an "elective" cesarean with women of that size.

However, little research exists to support this idea. Instead, doctors are relying on their biases and their fears when making the decision about planned vaginal vs. planned cesarean births in this group.  The bottom line is that most don't believe that "extremely obese" women CAN birth vaginally, that vaginal birth in fat women is extremely dangerous when it does happen........so a planned cesarean is assumed to be safer for this group.

A new study finally questions this assumption and actually collects data on this issue. 

It showed that a policy of routine cesarean delivery in supersized women does NOT improve outcomes, and that most women with "extreme obesity" can birth vaginally.  It concludes that decisions about planned cesareans in very fat women should be made on an individual circumstances, just as it is with other women. 

Study Details

This is a very strong study, done nationwide in the UK as part of their National Health Service (NHS).  You need that kind of nationwide study because there usually aren't all that many women with BMI greater than 50 (the definition of "extreme obesity" in this study) in any one hospital or even any one region.  In order to have robust findings, you need data from a large group of hospitals, with a large sample of women who fit the study's parameters. Even in a nationwide study like this, the study group size was only 591, but that's as robust a study group as you are likely to get in research on this population.

Of the 591 women with BMI greater than 50, 174 had a planned cesarean, compared to 417 who were in the planned vaginal delivery group.  The study then tracked the outcomes of each group.

[It's damning with faint praise to have to say this, frankly, but lukewarm kudos to the NHS for planning a vaginal delivery for most (70%) of these "extremely obese" women ─ this wouldn't happen in many areas of the USA.  The trend here is simply to automatically schedule most supersized women for a cesarean.]

Considerably warmer kudos to the NHS for the fact that of those supersized women who planned a vaginal delivery, 70% actually achieved a vaginal delivery. 

Yes, you read that correctly.  70%, or nearly 3 in 4 of women with a BMI greater than 50, actually had a vaginal birth when given the chance to labor.

This is extremely different than what most doctors believe about a "morbidly obese" woman's ability to give birth vaginally. And I'd bet good money that the UK's vaginal birth rate in this group could be even better if they induced less.

Even so, that's far better than the US rates. Compare the NHS's 30% c-section rate in women with BMI over 50 to US studies. For example, Weiss (2004) and Dietz (2005), both very large, multi-hospital studies in the USA, found a nearly 50% c-section rate in women  with BMI greater than 35 ─ in first-time mothers!

Do you really think that the uteri of British women are that much more efficient?  A ~20% lower c-section rate, despite a BMI starting more than 15 points higher? 

Doctors like to assume that cesarean rates in morbidly obese women are due solely to maternal factors, like "poor contractility" or "soft tissue dystocia" (a.k.a. fat vaginas). 

But obviously, physician management has much more to do with cesarean rates in very fat women, or the cesarean rate in high-BMI women would be consistent between countries and over time. 

Nitpicks About The Study

Overall, it's a pretty decent study, but I would nitpick a few things.

First of all, their multivariate model of risk factors for cesarean in labor did not even address induction (!), which is probably one of the biggest drivers of a high c-section rate in women, let alone women of size.  Study after study shows an extremely high rate of inductions in women of size, yet rarely do studies control for this factor.  Connect the dots, people!  (More on this below.)

The study could also have used a lot more information on how the labors of "extremely obese" women were managed, especially in comparison with the labors of non-obese women.  Furthermore, it might have been quite illuminating to compare the labors and physician management of those high-BMI women who ended up with a cesarean after labor to those who ended up with a vaginal birth.  Why aren't we evaluating and discussing how to improve vaginal birth rates in high-BMI women instead of just clutching our pearls and lamenting cesarean rates in this group?

Don't get me wrong; the study was ground-breaking and pretty amazing for the generally fat-phobic world of obstetrics.  But I wish they would go beyond the simplistic and get into more substantial evaluation of the deeper questions these studies bring up.

The main negative finding in the study was the fact that the "extremely obese" women in the vaginal birth group had a shoulder dystocia rate of 3.1%, which is higher than the rate reported in an unselected population (0.6%).  Fear of shoulder dystocia and related birth injuries causes many doctors to promote planned cesareans for women of size, but it's important to note that NONE of the babies involved experienced permanent injury so the finding is of questionable importance.  Also, some studies that control for fetal size and diabetic status have found that once these are accounted for, obesity is not associated with shoulder dystocia. So it's ridiculous to mandate a cesarean for supersized women simply out of fear of shoulder dystocia and birth injuries.

Furthermore, if they wanted to reduce the shoulder dystocia rate in this group, I bet they could do so by "allowing" them more mobility during labor, encouraging alternative positioning instead of the "stranded beetle" position, inducing less often, discouraging early epidural placement, and avoiding forceps/vacuum extraction more often.

The answer to shoulder dystocia concerns is not more cesareans, but rather exploring preventive management during labor and improving SD management if it does occur.

Another negative finding in the study is that almost no supersized women tried for for a VBAC, and of the few who did, the success rate was very low (9 of 26, or 35%).  The study notes that the VBAC rate in some studies is low in women of size, implying that there is little reason to allow a trial of labor in this group. However, they fail to note that these studies have extremely high rates of induction, which is known to lower the VBAC success rate substantially, nor did they note how many of the women in this study were induced in their attemtped VBAC. We have yet to have a really good-quality study of VBAC in "morbidly obese" women, one in which these women were given a reasonable chance at VBAC with a spontaneous trial of labor.  It is FAR too soon to be making sweeping judgments about who should and should not be "allowed" a trial of labor.

The lack of recognition of the negative role that induction plays in the birth outcomes of high-BMI women is tremendously frustrating to me and remains one of my pet peeves in this type of research. Even this study ignores it.  Sigh.

On a happier note, one positive finding was that the study did not find any statistically significant differences in anesthetic, maternal or neonatal complications between the planned vaginal and planned cesarean groups, except the occurrence of shoulder dystocia (again, none of whom experienced permanent injury).  This belies the common perception that outcomes are poorer when vaginal delivery is "allowed" in supersized women. 

It's important to note that the rate of composite major maternal morbidity was higher in the planned cesarean group (6.3% vs. 4.3%), but alas, the difference did not rise to statistical significance.  With a larger study, chances are it would have.

Cesareans are an important risk factor for hemorrhage, blood clots, infection, wound comlications, and admission to Intensive Care, especially in this group.  Therefore, it's indefensible to automatically expose supersized women to these complications across the board, based on their weight alone.

Conclusions

Finally, the commentary by S Quenby that accompanied this study was interesting. 

A consequence of this data [about complications among obese women] is the frequently voiced opinion at midwifery, obstetric and anaesthetic conferences that the safest way to deliver a women with a body mass index (BMI) over 50 kg/m2 may be by elective CS. This elective option has been proposed as a way of avoiding the known risks of vaginal delivery and emergency CS in this population.

[This study] challenge[s] the assumption that elective CS is safer than planned vaginal delivery in these morbidly obese women. A large proportion, 70% of women with BMI [greater than] 50 kg/m2, who had a planned vaginal delivery did indeed deliver vaginally without the expected increase in neonatal and postnatal complication rates compared with those with planned elective CS.

These data strongly indicate that elective CS in morbidly obese women cannot be justified, except for the usual obstetric indications. Only in very unusual circumstances should elective caesarean be performed if the requisite obstetric indications are not present.

Doctors need to STOP automatically scheduling cesareans for supersized women on the basis of their weight alone. 

Planned cesareans do NOT improve outcomes in this group, and there was a trend towards poorer outcomes with planned cesareans. 

Furthermore, contrary to what many doctors believe, this study shows that very fat women CAN give birth vaginally if given an adequate chance to do so.  It's about time we let them.

*Image above of obese cesarean from BMJ 2006 study on "Obesity and Reproduction," courtesy of Pubmed.


Study abstract

Homer CS, Kurinczuk JJ, Spark P, Brocklehurst P, Knight M.   Planned vaginal delivery or planned caesarean delivery in women with extreme obesity.  BJOG. 2011 Mar;118(4):480-7. doi: 10.1111/j.1471-0528.2010.02832.x. Epub 2011 Jan 18

National Perinatal Epidemiology Unit, University of Oxford, UK.

Abstract

OBJECTIVE: To compare the outcomes of planned vaginal versus planned caesarean delivery in a cohort of extremely obese women (body mass index ≥ 50 kg/m(2)).

DESIGN: A national cohort study using the UK Obstetric Surveillance System (UKOSS).

SETTING: All hospitals with consultant-led maternity units in the UK.

POPULATION: Five hundred and ninety-one extremely obese women delivering in the UK between September 2007 and August 2008.

METHODS: Prospective cohort identification through UKOSS routine monthly mailings.

MAIN OUTCOME MEASURES: Anaesthetic, postnatal and neonatal complication rates.

RESULTS: After adjustment, there were no significant differences in anaesthetic, postnatal or neonatal complications between women with planned vaginal delivery and planned caesarean delivery, with the exception of shoulder dystocia (3% versus 0%, P = 0.019). There were no significant differences in any outcomes in the subgroup of women who had no identified medical or antenatal complications.

CONCLUSIONS: This study does not provide evidence to support a routine policy of caesarean delivery for extremely obese women on the basis of concern about higher rates of delivery complications, but does support a policy of individualised decision-making on the mode of delivery based on a thorough assessment of potential risk factors for poor delivery outcomes.

PMID: 21244616