Abstract
Introduction
Pregnant people with obesity are more likely than those without obesity to undergo induction of labor and to require unplanned cesarean delivery during induction at term. Whether they are more likely to undergo unplanned cesarean delivery during preterm induction of labor is unknown. This study examines the induction of labor success among people with obesity undergoing indicated late preterm induction of labor.
Methods
This is a secondary analysis of a multicenter, randomized trial of betamethasone versus placebo among pregnancies at risk for late preterm delivery, defined as delivery between 34 weeks and 0 days and 36 weeks and 6 days between 2010 and 2015. This study included pregnant people with live singleton nonanomalous gestations at high risk for late preterm delivery before 36 weeks and 6 days. This secondary analysis included all participants who underwent a medically indicated preterm induction of labor starting before 36 weeks and 5 days. We excluded participants who underwent planned cesarean delivery, had spontaneous labor, or had a body mass index (BMI) <18.5. We compared final delivery mode among participants undergoing preterm induction stratified by obesity class: no obesity (BMI 18.5–29.9), class 1 obesity (BMI 30–34.9), class 2 obesity (BMI 35–39.9), and class 3 obesity (BMI ≥ 40). The primary outcome was cesarean delivery.
Results
Of 1236 included participants, 482 were not obese, while 754 had obesity: 288, 220, and 246 with class 1–3 obesity, respectively. Among the obese participants, the overall vaginal delivery rate was 69.9% (527/754). In a univariable analysis, participants with obesity were more likely to undergo cesarean delivery than their nonobese counterparts (p < 0.0001). In an adjusted multivariable analysis, participants with class 1–3 obesity were more likely to undergo cesarean delivery than their nonobese counterparts (class 1, adjusted odds ratio (aOR) 1.62, 95% confidence interval [CI] 1.12–2.36; class 2, aOR 2.30, 95% CI 1.55–3.41; class 3, aOR 2.96, 95% CI 2.02–4.33).
Conclusions
People with obesity are more likely to undergo cesarean delivery during medically indicated late preterm induction, and risk increases with BMI class. However, the majority still deliver vaginally. Further studies are needed to understand differences in labor and induction physiology among pregnant people with obesity.