Cervical ripening balloon vs oral misoprostol for induction of labor in small‐for‐gestational age: retrospective multicenter study

ABSTRACT Objective To compare the maternal and neonatal outcomes following induction of labor (IOL) using oral misoprostol vs mechanical cervical ripening using a cervical ripening balloon (CRB) in singleton pregnancies complicated by small‐for‐gestational age (SGA), including those with late‐onset fetal growth restriction (FGR). Methods This was a retrospective multicenter cohort study of women with a singleton pregnancy with estimated fetal weight < 10 th percentile and a Bishop score of < 7, who underwent IOL ≥ 37 weeks' gestation for suspected SGA or late‐onset FGR in one of three European tertiary centers. Participants were assigned to one of two groups depending on whether they underwent cervical ripening using a CRB without pharmacologic agents (CRB‐only group) or received oral misoprostol with or without a CRB (misoprostol group). Women who had had a prior Cesarean delivery (CD), those who received vaginal misoprostol and those with early‐onset FGR, fetal structural anomalies or contraindications to vaginal delivery were excluded. The primary outcome was CD. Secondary outcomes included spontaneous vaginal delivery (SVD) within 24 h after starting IOL, operative vaginal delivery (OVD), oxytocin augmentation, uterine tachysystole and neonatal outcomes. Inverse probability of treatment weighting was used to account for baseline differences and doubly robust estimation was used to adjust for confounders. Results A total of 848 women was included in the analysis, of whom 431 (50.8%) received a CRB only and 417 (49.2%) received oral misoprostol with or without a CRB. Baseline characteristics differed between the two groups, with women in the misoprostol group being older, more often nulliparous and undergoing IOL later in gestation. After adjustment, there was no significant difference in the rate of CD between the two groups (adjusted odds ratio (aOR), 1.29 (95% CI, 0.82–2.04)). Women receiving misoprostol were significantly less likely to undergo OVD (aOR, 0.33 (95% CI, 0.18–0.64)) or require oxytocin augmentation (aOR, 0.04 (95% CI, 0.03–0.07)) compared with the CRB‐only group. SVD within 24 h after starting IOL was also less likely in the misoprostol group (aOR, 0.49 (95% CI, 0.33–0.74)). Uterine tachysystole occurred more frequently in the misoprostol ± CRB group, but this was not associated with higher rates of CD for fetal distress or adverse neonatal outcomes. The rate of admission to the neonatal intensive care unit was similar between the two groups. Subgroup analysis in pregnancies with confirmed late‐onset FGR yielded comparable findings. Conclusions In pregnancies complicated by late‐onset FGR or SGA, oral misoprostol did not increase the risk of CD compared with mechanical cervical ripening only, and was associated with a reduced need for operative interventions and labor augmentation. These findings support the use of oral misoprostol as a safe and effective option for IOL in this high‐risk population. Randomized controlled trials are needed to confirm these results. © 2025 International Society of Ultrasound in Obstetrics and Gynecology.