Risk factors for failed induction of labor among pregnant women with Class III obesity.

Introduction: Our aim was to identify risk factors for failed induction in morbidly obese patients undergoing the induction of labor at term.

Material And Methods: This was a retrospective multicenter study on a cohort of 235 patients with a body mass index greater than 40 kg/m and giving birth to a singleton in cephalic presentation, who had an induction of labor from 38 weeks of amenorrhea. Scheduled cesareans and spontaneous vaginal deliveries were excluded. Maternal, peri-partum and neonatal characteristics were analyzed according to the delivery route.

Results: In all, 235 patients were included. Of these, 62.5% patients delivered vaginally and 37.5% by cesarean section. The frequency of nulliparity was greater in patients who had a cesarean section (56 [interquartile range, IQR, 38.1] vs 56 [IQR 63.6], P < .001). In multivariate analysis, nulliparity (odds ratio [OR] 2.81, 95% confidence interval [CI] 1.58-4.97], P < .001), low Bishop's score (OR .794, 95% CI .70-.90, P < .001) and weight gain (OR 1.04, 95% CI 1.01-1.08, P = .033) were independent risk factors for failed induction. Umbilical cord pH at birth lower than 7 (0 vs 7 [IQR 8.0], P < .001) and lower than 7.20 (36 [IQR 24.5] vs 35 [IQR 39.8], P = .014) as well as the Apgar at 1 minute (14 [IQR 9.5] vs 17 [IQR 19.3], P = .032) was significantly higher in infants born by cesarean section.

Conclusions: In this cohort, 63% of women with Class III obesity had successful inductions of labor; risk factors for failed induction include nulliparity and unfavorable Bishop score.