Cervical balloon catheter versus Dilapan-S for outpatient cervical ripening: A randomized controlled trial.

Background: As induction of labor increases in the United States, safe, effective outpatient cervical ripening has been explored as a method to decrease the inpatient time burden. The most effective method of outpatient mechanical cervical ripening remains unclear.

Objective: To evaluate if Dilapan-S is non-inferior to cervical balloon for outpatient cervical ripening (CR) based on change in Bishop score.

Study Design: This was a single-blind, randomized controlled trial at a single tertiary hospital. Term patients, both nulliparous and multiparous, aged 18-50 with a singleton, cephalic fetus and no prior c-section who were scheduled for outpatient CR per pre-existing hospital policy were eligible. Participants were randomized to single balloon cervical ripening with a Cook catheter with 60mL in the intrauterine balloon or placement of 3 to 5 Dilapan-S hydroscopic dilators and were then discharged home. On return to the hospital, the CR agent was removed, a blinded cervical exam performed, and participants completed a satisfaction survey. Further induction proceeded per their obstetrical provider. The primary outcome was change in Bishop score. Secondary outcomes included patient satisfaction, mode of delivery, induction time, adverse maternal and neonatal outcomes and a cervical ripening failure composite (failure to place randomized cervical ripening agent, prelabor rupture of membranes prior to scheduled return to hospital, significant vaginal bleeding, or need for further cervical ripening after the initial agent is removed) .We had 80% power to show non-inferiority in change in Bishop score with a margin of 2 and standard deviation of 3.

Results: From May 2022 to June 2023, 80 participants were randomized with no difference in baseline demographic data, starting dilation, or Bishop score. 70% of participants in each arm were nulliparous. There was no difference in change in Bishop score between Dilapan-S and cervical balloon (median change 3 (interquartile range (IQR) 2-5) vs 3 (IQR2-4.5) respectively, p=0.91). There was no difference in time to delivery, mode of delivery, or maternal or neonatal outcomes. Participants randomized to Dilapan-S were more satisfied with their experience (satisfaction scale 0-10, median 9 (IQR 8-10) vs 8 (IQR 5-9), p<0.01) and were less likely to experience cervical ripening failure (7(17.5%) vs 18(45%), p<0.01) compared to participants who were randomized to cervical balloon.

Conclusions: Dilapan-S was non-inferior to cervical balloon catheter for outpatient cervical ripening based on change in Bishop score. Participants were more satisfied with Dilapan-S and less likely to experience cervical ripening failure compared to a cervical catheter with single balloon inflation.