Association of Early Amniotomy After Foley Balloon Catheter Ripening and Duration of Nulliparous Labor Induction

OBJECTIVE: To evaluate the association between early amniotomy after ripening with a Foley balloon catheter and duration of labor induction. METHODS: In this retrospective matched cohort study, 546 nulliparous women with a singleton viable gestation undergoing cervical ripening with a Foley balloon catheter were compared based on timing of amniotomy after catheter removal: early (defined as artificial rupture of membranes less than 1 hour after Foley removal) compared with no artificial rupture of membranes in the first hour. Women in the early amniotomy group were matched to women in the control group according to health care provider type, cervical examination after Foley removal, and indication for induction in a one-to-one ratio. Bivariable and multivariable analyses were performed to determine whether early amniotomy was associated with vaginal delivery within 24 hours and other adverse maternal and neonatal outcomes. Cox proportional hazard regression was used to compare time intervals from catheter removal to complete dilation and from catheter removal to delivery. RESULTS: In univariable analysis, the frequency of vaginal delivery within 24 hours of Foley placement was higher in women with early amniotomy (42.9% compared with 33.0%, P =.02). The median time intervals from Foley catheter removal to complete dilation (9.0 hours compared with 12.1 hours) and to delivery (10.6 hours compared with 13.8 hours) were also significantly shorter for women who underwent early amniotomy ( P <.001 for both). There were no significant differences in any other adverse maternal or neonatal outcomes. In multivariable analysis, early amniotomy remained associated with higher odds of vaginal delivery within 24 hours and shorter times from catheter removal to complete dilation and to delivery. CONCLUSION: Early amniotomy after Foley balloon catheter removal is associated with shorter duration of labor induction among nulliparous women.