Friday, November 21, 2014

Increase in Cesarean Rate in Morbidly Obese Women Over Time

Here's the abstract of an interesting new study. I haven't seen the full text yet but it appears to show that while the cesarean rate has gone up over time in all sizes of women, it's gone up the most in the higher BMI categories.

In other words, a high BMI woman is far more likely to have a cesarean now than she was in 1990.

This shows that the high cesarean rate in obese women is not just about obesity itself, but also how obese women are managed in labor and the lowering of the surgical threshold for performing cesareans in high BMI women.

I've been saying this for years. Some care providers like to pretend that the high cesarean rate in obese women is only about the woman's fatness, as if this somehow prevents a fat woman from giving birth vaginally (the classic "fat vagina" theory).

But if it was really only about physical barriers, then you would see a relatively consistent cesarean rate in this group over time, and you DON'T. This study shows that there used to be much lower cesarean rates in women of size than there is today, and older studies show that the cesarean rate wasn't always higher in obese women than in average-sized women.

Critics would point out that the cesarean rate has increased in all groups over time, not just in obese women. Sad, but true.

But the cesarean rate has not increased equally in every group, as this study points out. Look at their comparison of cesarean rates between 1990 and 2012 by BMI group*:

                              1990                     2012                   Increase

Underweight         14.4%                   27.9%                  13.5%
Normal                  16.1%                   31.4%                  15.3%
Overweight           19.5%                   38.8%                  19.3%
Obese I                 22.3%                   45.1%                  22.8%
Obese II                25.0%                   50.2%                  25.2%
Obese III               26.9%                   55.2%                  28.3%

The increase in cesarean rates was not uniform across BMI categories. The increase in "normal" weight women was 15.3%, but the increase in Obese Class III women was nearly twice that at 28.3%.

In 1990, Obese class III women had a 26.9% cesarean rate in 1990....just over 1 in 4.

In 2012, Obese Class III women  had a 55.2% cesarean rate instead, or more than 1 in every 2 "morbidly obese" women.

In just 22 years, the cesarean rate in Class III Obese women went from 26.0% to 55.2%. How far will it go in the next 20 years?

Something has changed...and that something is probably how those women are managed in labor (more interventions), the exaggeration of fear around their pregnancies, and the resulting lowering of the surgical threshold for a cesarean in that group.

Similarly, research shows that cesarean rates in the same BMI group can vary dramatically between locations. For example, recent studies from Tennessee and Kentucky show an abysmal cesarean rate of nearly 60% in "morbidly obese" women. One particularly appalling study from Michigan shows a cesarean rate of over 80% in women with a BMI over 50.

Yet a large study from the U.K. shows a cesarean rate of about 30% in the same population.

This shows that practice variation is an issue not only in the overall population, but perhaps particularly in high BMI women.

It's time for care providers to examine not only how to prevent questionable cesareans in women across the board, but also to focus on how to prevent questionable cesareans in high-BMI women. Given that cesareans carry more risks in women of size, especially multiple repeat cesareans, it's inexcusable to be exposing so many of these women to these risks unnecessarily.

The cesarean rate is high is women of size, but the variation in rates over time and between locations shows it doesn't have to be, and that there are things we could be doing to bring the cesarean rate down in this group.

It's long past time to be looking into that question. Some researchers are starting to ask these questions or propose solutions, but few have actually tested these theories.

Where are the researchers and providers willing to actually study how to lower the cesarean rate in women of size?


J Perinat Med. 2014 Jun 10. pii: /j/jpme.ahead-of-print/jpm-2014-0126/jpm-2014-0126.xml. doi: 10.1515/jpm-2014-0126. [Epub ahead of print] Impact of maternal body mass index on the cesarean delivery rate in Germany from 1990 to 2012. Kyvernitakis I, Köhler C, Schmidt S, Misselwitz B, Großmann J, Hadji P, Kalder M. PMID: 24914711
ABSTRACT AIMS: Maternal obesity is a risk factor for cesarean delivery (CD). The aim of this analysis was to determine the association between early-pregnancy body mass index (BMI) and the rate of CD over the past two decades. METHODS: We retrospectively analyzed data from the perinatal quality registry of singleton deliveries in the state of Hesse in Germany from 1990 to 2012. We divided the patients into groups according to the WHO criteria for BMI: underweight (<18.5), normal weight (18.5-<25), overweight (25-<30), obese class I (30-<35), obese class II (35-<40), and obese class III (≥40). RESULTS: The analysis included 1,092,311 patients with available data regarding maternal BMI and mode of delivery. The CD rates for underweight (<18.5), normal weight (18.5-<25), overweight (25-<30), obese class I (30-<35), obese class II (35-<40), and obese class III (≥40) women increased from 14.4%, 16.1%, 19.5%, 22.3%, 25%, and 26.9% in the year 1990 to 27.9%, 31.4%, 38.8%, 45.1%, 50.2%, and 55.2% in the year 2012, respectively (P<0.001). CONCLUSION: Maternal BMI in early pregnancy is linearly associated with the incidence of CD. We found a disproportionate increase of CD in morbidly obese women compared with the CD incidence in the reference BMI population over the past two decades.

* Standard BMI classifications: 

  • "Underweight" = BMI less than 18
  • "Normal" weight = BMI 18-24.9
  • "Overweight" = BMI 25-29.9
  • Class I Obese = BMI 30-34.9
  • Class II Obese = BMI 35-39.9
  • Class III Obese = BMI of 40 plus
  • "Super Obese" = BMI of 50 plus

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