Impact of pre-pregnancy obesity on cesarean delivery rates in nulliparous pregnant people undergoing induction of labor

Objective To evaluate the impact of pre-pregnancy obesity on the cesarean delivery rate in nulliparous pregnant people undergoing induction of labor. Study design This is a retrospective cohort study of nulliparous pregnant people with a normal weight and obesity who underwent induction of labor between 37 and 41 weeks gestation at a single institution from 2012 to 2018. Weight category was based on pre-pregnancy body mass index. The primary outcome was rate of cesarean delivery. Additional demographic and clinical characteristics were analyzed. A chi square test was used to compare the cesarean delivery rates. Multivariate logistic regression was used to generate adjusted odds ratios (aOR) and 95% confidence intervals (CI) controlling for potential cofounders. Results Of the 557 pregnancies identified, 88/285 (31%) of pregnant people with a normal weight had a cesarean delivery while 165/263 (63%) of pregnant people with obesity had a cesarean delivery (cOR 3.8, 95% CI 2.6-5.4). After adjustment, pregnant people with obesity remained more likely to have a cesarean delivery compared to pregnant people with a normal weight (aOR 2.7, 95% CI 1.8-4.0). Further, cesarean delivery was more likely in those with an unfavorable modified Bishop score (aOR 3.4, 95% CI 1.8-6.5) and gestational weight gain above the Institute of Medicine recommendation (aOR 2.6, 95% CI 1.8-3.9). The rate of cesarean delivery was not different by class of obesity (p = .32). Conclusion Pre-pregnancy obesity is associated with higher cesarean delivery rates in nulliparous pregnant people undergoing induction of labor compared with normal pre-pregnancy body mass index. Gestational weight gain above the Institute of Medicine recommendations and having an unfavorable modified Bishop score at the time of induction are associated with increased cesarean delivery rates.