491: The efficacy of early amniotomy after ripening with Foley balloon catheter in nulliparous labor induction

Abstract

To evaluate the association between early amniotomy after ripening with foley balloon catheter and duration of labor. In this retrospective cohort study, 426 nulliparous women with a singleton viable gestation undergoing cervical ripening with foley balloon catheter were compared based on timing of amniotomy after catheter removal: early (defined as artificial rupture of membranes less than 1h after foley removal) versus no artificial rupture of membranes in the first hour. Women were excluded if spontaneous rupture of membranes occurred while foley was in place. Bivariable and multivariable analyses were performed to determine whether early amniotomy was associated with vaginal delivery within 24 hours, chorioamnionitis, and other 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. In univariable analysis, women who underwent early amniotomy had a slightly more favorable cervical exam after foley removal (modified Bishop score of 4.9 ± 1.4 vs. 4.0 ± 1.4, p<.001) but otherwise had similar characteristics including gestational age at delivery (40.2wk ± 1.2 vs. 40.3wk ± 1.3, p=0.674). The frequency of vaginal delivery within 24h was higher in women with early amniotomy (45.5% vs. 33.3%, p=0.010) with no significant difference in the frequency of cesarean delivery (46.0% vs. 49.3%, p=0.497). The median time intervals from foley catheter removal to complete dilation (8.2h vs. 12.2h) and to delivery (10.9h vs. 14.4h) were also significantly shorter for women who underwent early amniotomy (p<.001 for both). While there was no significant difference in rate of chorioamnionitis between groups (19.0% vs. 20.3%, p=0.731), there were fewer NICU admissions for neonates of women who underwent early amniotomy (6.1% vs. 13.6%, p=0.009). In multivariate analysis, after adjusting for potential confounding factors, early amniotomy remained associated with higher odds of vaginal delivery within 24h, fewer NICU admissions, and shorter times from catheter removal to complete dilation and to delivery (Table). Early amniotomy after foley balloon catheter removal is associated with shorter duration of labor induction and fewer NICU admissions.