To assess the risk factors associated with cesarean delivery in women with class III obesity (body mass index [BMI, calculated as weight in kilograms divided by height in meters squared] 40 or higher) who are undergoing induction of labor.
This was a retrospective cohort of obese women with a BMI of 40 or higher and singleton pregnancy of 34 weeks of gestation or longer who underwent induction of labor at two large teaching institutions from January 2013 to December 2015. The primary outcome was cesarean delivery. Secondary outcomes included maternal and neonatal composite morbidity. We then assessed the applicability of using a previously developed calculator to predict the risk of cesarean delivery. The area under the receiver operating characteristic (ROC) curve was used as a measure of the ability of the calculator to discriminate between women who underwent cesarean compared with vaginal delivery.
There were 485 women with class III obesity who underwent induction during the study period. Of the 428 women who met inclusion criteria, 81.8% had a BMI of 40–50, 14.5% had a BMI of 50–60, and 3.7% had a BMI higher than 60. The overall cesarean delivery rate was 49.1% (46% with BMI 40–50, 63% with BMI 50–60, and 69% with BMI higher than 60, P=.012). Of the 428 women studied, 77.6% were black and 55% were nulliparous. Nulliparity, height, initial cervical dilation, and modified Bishop score were associated with a higher rate of cesarean delivery in multivariable models. Maternal and neonatal composite morbidity was higher in obese women who underwent cesarean delivery, compared with those who delivered vaginally. The performance of a previously developed induction calculator applied to this cohort had an area under the ROC curve of 75% (95% CI 0.70–0.79).
In women with class III obesity who underwent labor induction, the cesarean delivery rate approaches 50%. Nulliparity, height, and unfavorable cervical examination were the most significant risk factors for cesarean delivery. This information can be used to augment counseling for the obese patient who is undergoing induction.