30 mL Single- versus 80 mL double-balloon catheter for pre-induction cervical ripening: a randomized controlled trial

Objective: To compare the efficacy of an 80mL double-balloon catheter versus a 30mL single-balloon catheter for pre-induction cervical ripening.Methods: We performed a randomized controlled trial of women 18 years with a singleton, vertex pregnancy, a reactive non-stress test, and a Bishop score 5 comparing an 80mL double- versus a 30mL single-balloon catheters for cervical ripening. Women were randomly assigned to the two catheter types, stratified 1:1 by nulliparity or multiparity. The primary outcome was achieving a Bishop score 6 at the time of catheter expulsion or removal assessed by chi-squared, stratified by parity.Results: A total of 98 women were included in the analysis (50 in the 80mL double and 48 in the 30mL single-balloon catheter groups). Among nulliparous women, a greater proportion of those randomized to the 80mL double achieved a Bishop score 6 at time of catheter removal (88.0% versus 28.0%; p0.001) and delivered vaginally (60.0% versus 32.0%; p=0.047) compared to those with the 30mL single-balloon catheter. We found no difference by catheter type in achieving a Bishop score 6 or vaginal delivery among multiparous women.Conclusions: These findings suggest the 80mL double-balloon catheter is more effective than the 30mL single-balloon catheter for pre-induction cervical ripening and achieving a vaginal delivery in nulliparous women.