Characterizing vaginal misoprostol induction in individuals with and without severe obesity

To compare labor induction characteristics and delivery outcomes among individuals with body mass index < 40 versus ≥ 40 kg/m² undergoing induction at term.

This secondary analysis utilized data from the vaginal misoprostol arm of a cluster randomized controlled trial comparing vaginal to oral misoprostol for induction. Individuals at ≥ 37 weeks gestation with cervical dilation ≤ 2 cm undergoing induction using a standardized protocol were included. Vaginal misoprostol was given in 25 µg doses every three hours for up to five doses, followed by a standardized oxytocin protocol. We compared labor progression among individuals with BMI < 40 and ≥ 40 kg/m² at delivery, including labor duration, misoprostol use, and obstetric and neonatal outcomes. Generalized estimating equations were used to account for clustering and comorbid conditions. Effect sizes were presented as odds ratios and adjusted mean differences with 95% confidence intervals.

From May 2021 to September 2022, 1,322 patients received vaginal misoprostol for labor induction at term. Among these, 1,058 (80.0%) had a BMI < 40 kg/m² and 264 (20.0%) had a BMI ≥ 40 kg/m². Individuals with severe obesity were more likely to start induction with a closed cervix. After adjustment for clustering, initial cervical dilation, hypertension, and diabetes, inductions in the group with severe obesity had longer total durations (adjusted mean difference 3.5h, 95% CI 1.9-4.8), first stage of labor (adjusted mean difference 2.2h, 95% CI 0.6-3.8), and duration of oxytocin use (adjusted mean difference 2.5, 95% CI 1.1-3.8). Individuals with BMI ≥ 40 kg/m² also had lower odds of vaginal delivery (aOR 0.6, 95% CI 0.4-0.8) and required more doses of misoprostol for induction.

Severe obesity, defined as BMI ≥ 40 kg/m², is associated with longer time to delivery, increased misoprostol requirement, longer duration of oxytocin use, and lower odds of vaginal delivery compared to individuals with lower BMI. Consideration of alternative labor induction protocols must be balanced with increased comorbidities and overall obstetric morbidity in this group.