(HealthDay News) – For extremely obese women, predictors of cesarean delivery (CD) include body mass index (BMI), as well as maternal age, parity, and cervical dilation at the time of admission, according to a study published in the December issue of the American Journal of Obstetrics & Gynecology.

To investigate predictors of CD, Ravindu P. Gunatilake, MD, from the Duke University Medical Center in Durham, NC, and colleagues identified all pregnant women delivering at a single institution from Jan. 1, 2008, through July 31, 2010, weighing >275 lb at the time of delivery and undergoing a trial of labor (TOL) with a singleton gestation of more than 34 weeks.

Of the 357 pregnant women who weighed more than 275 lb (all with a BMI of >40kg/m²), 69.5% attempted a TOL. The researchers found that, compared to those having a vaginal delivery, women who underwent CD had a significantly greater BMI (51.6 vs. 49.9kg/m²; P=0.038), were less likely to be parous (32.2% vs. 65.8%; P<0.0001), and were more likely to be induced (80.5% vs. 57.8%). Among nulliparous women, independent predictors of CD included maternal age, parity, and cervical dilation at time of admission, in multivariate analysis. The odds of CD were also increased 3.5-fold with an increase in BMI of 10kg/m² (P=0.002).

“Among nulliparous extremely obese women attempting a TOL, BMI was an independent predictor of CD, with the rate of CD increasing further with increasing BMI,” the authors write. “The underlying mechanisms for failed TOL in the setting of maternal obesity remain largely unknown.”

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