Mechanical cervical ripening with transcervical balloons significantly shortens labor duration compared to oral misoprostol in pregnancies with elevated BMI.

Effective cervical ripening is crucial for successful labor induction, yet it presents unique challenges in pregnancies with elevated body mass index (BMI). Women with higher BMI often experience longer labor durations and increased risks of complications, making the choice of induction method particularly important. Current standard-of-care options include mechanical methods like transcervical balloons and pharmacological agents such as misoprostol, a prostaglandin E1 analog. This study addresses the gap in understanding which method offers superior efficacy in this specific, high-risk population, aiming to optimize induction protocols.

A retrospective single-center cohort study (2022-2024) at Montpellier University Hospital compared cervical ripening methods in 247 singleton term pregnancies (37-42 weeks) with cephalic presentation, BMI ≥ 25 kg/m2, and Bishop score < 6. Participants received either a transcervical balloon or oral misoprostol (25 µg/2h or 50 µg/4h). Researchers used survival analysis to assess the induction-to-delivery interval and logistic regression for vaginal delivery rates, adjusting for key covariates. Exclusion criteria included maternal age < 18 years, scarred uterus, or low-lying placenta.

Among 247 eligible patients, 180/247 (72.9%) achieved vaginal delivery, with 21/180 (11.7%) being operative vaginal deliveries, and 67/247 (27.1%) resulting in caesarean sections. No statistically significant difference in caesarean rates was observed between groups, though the study was not powered for this equivalence. The transcervical balloon method achieved significantly shorter induction-to-delivery intervals (Mean 25.5 h; 95%CI 23.8-27.2 h) compared to oral misoprostol (Mean 35.3 h; 95%CI 33.0-37.6 h; p < 0.001). This represents a 9.8-hour reduction in labor duration. Induction-to-active-phase intervals were also shorter with balloons (Mean 21.1 h; SD 12.8 h) versus misoprostol (Mean 30.3 h; SD 17.7 h; p < 0.001). No differences were found in first active-stage or second-stage duration, or between different misoprostol regimens. Cox regression identified several predictors of longer induction-to-delivery: nulliparity (HR: 0.31; 95%CI 0.22-0.42), misoprostol use (HR: 0.46; 95%CI 0.33-0.66) compared to intrauterine balloons, large for gestational age (LGA) (HR: 0.63; 95%CI 0.43-0.92), higher BMI (HR: 0.97; 95%CI 0.97-1.00), and excessive weight gain (HR: 0.98; 95%CI 0.95-1.00). A Fine and Gray competing-risks model further confirmed that mechanical ripening provided shorter time intervals from induction to delivery (p = 0.033) and to active phase (p = 0.003).