Objective: To estimate the effect of maternal body mass index (BMI) on progress and outcomes of prostaglandin labor induction.
Methods: This study was a secondary analysis of data collected during the Misoprostol Vaginal Insert Trial, a multisite, double-blind, randomized trial of women requiring cervical ripening before induction of labor. The duration, characteristics, and outcomes of labor were analyzed after stratification by BMI categories. Multivariable regression analysis was performed on all outcomes of interest, adjusting for race, parity, and treatment group allocation.
Results: One thousand two hundred seventy-three patients were stratified according to BMI categories, with 418 study participants classified as lean (BMI less than 30), 644 as obese (BMI 30-39.9), and 211 as extremely obese (BMI 40 or higher). The incidence of cesarean delivery increased from 21.3% in the BMI less than 30 group to 29.8% in the BMI 30-39.9 group (odds ratio [OR] 1.57, 95% confidence interval [CI] 1.18-2.1, P=.002) and 36.5% in the BMI 40 or higher group (OR 2.12, 95% CI 1.47-3.06, P<.001). Median dose and duration of predelivery oxytocin in the lean group (2.6 units and 6.5 hours) was significantly lower than for women in either the obese (3.5 units and 7.7 hours) or the extremely obese (5.0 units and 8.5 hours) group. Median time to delivery was significantly longer in the BMI 40 or higher (27.0 hours) and BMI 30-39.9 (24.9 hours) groups compared with the BMI less than 30 (22.7 hours) group (P<.001). The relationship between maternal obesity and adverse labor and delivery outcomes persisted in a multivariable analysis that adjusted for race, parity, and treatment group allocation.
Conclusion: Duration of labor, oxytocin requirements, and cesarean delivery rates are significantly higher with increasing maternal obesity in prostaglandin-induced women.
Level of evidence: II.