Methods of induction of labor in women with obesity: A secondary analysis of two multicenter randomized controlled trials

Introduction: Obesity is an increasing public health concern worldwide and can lead to more complications in pregnancy and childbirth. Women with obesity more often require induction of labor for various indications. The aim of this study is to assess which method of induction of labor is safest and most effective in women with obesity.

Material and methods: This is a secondary analysis of two randomized controlled trials about induction of labor. Women with a term singleton pregnancy in cephalic presentation, an unfavorable cervix, intact membranes and without a previous cesarean section were randomly allocated to cervical priming with a Foley catheter or vaginal prostaglandin-E2-gel (PROBAAT-I) or a Foley catheter or oral misoprostol (PROBAAT-II). The inclusion and exclusion criteria for the studies were identical. Induction methods were compared in women with obesity (body mass index ≥30.0). Main outcomes were cesarean section and postpartum hemorrhage (blood loss >1000 mL).

Results: A total of 2664 women, were included in the trials, 517 of whom were obese: 254 women with obesity received a Foley catheter, 176 oral misoprostol and 87 prostaglandin E2 (PGE2). A cesarean section was performed in 29.1% of women allocated to Foley vs 22.2% in the misoprostol and 23.0% in the PGE2 groups. Comparisons between groups revealed no statistically significant differences: the relative risk [RR] was 1.31 (95% confidence interval [CI] 0.94-1.84) in the Foley vs misoprostol group and 1.27 (95% CI 0.83-1.95) in the Foley vs PGE2 group. The rates of postpartum hemorrhage were comparable (10.6%, 11.4% and 6.9%, respectively; P = 0.512). In women with obesity, more often a switch to another method occurred in the Foley group, (20.1% vs 6.3% in misoprostol vs 1.1% in the PGE2 group; P < 0.001). The risk of a failed Foley placement was higher in women with obesity than in women without obesity (8.3% vs 3.2%; adjusted odds ratio 3.12, 95% CI 1.65-5.90).

Conclusions: In women with obesity we found a nonsignificant trend towards an increased rate of cesarean sections in the group induced with a Foley catheter compared to oral misoprostol; however, the study lacked power for this subgroup analysis. The finding of a higher risk of failed placement of a Foley catheter in women with obesity can be used in shared decision making.