415: Early amniotomy in labor induction

Abstract

To investigate whether artificial rupture of membranes (AROM) < 4cm dilation is associated with the duration of labor induction and maternal and neonatal morbidity. Retrospective cohort study of 228,438 deliveries at 19 U.S. hospitals (Consortium on Safe Labor). We included women with a viable, singleton gestation who presented for labor induction at ≥ 37 weeks’ gestation with admission cervical dilation < 4cm. Women were compared by timing of AROM: early (AROM < 4cm dilation) versus not early. Women were excluded if SROM occurred < 4cm. Study group characteristics and outcomes were compared using chi-square, Mann Whitney U, and t-test as appropriate. Outcomes included duration of labor induction, cesarean delivery, composite maternal morbidity (uterine rupture, hysterectomy, blood transfusion, ICU admission, and death), and composite neonatal morbidity (sepsis, asphyxia, HIE, grade III or IV IVH, ICH, seizure, NEC, RDS, mechanical ventilation, and death). Cox proportional hazard regression was used to compare time intervals from induction to vaginal delivery. Logistic regression was used to estimate the independent effect of early AROM on cesarean, and maternal and neonatal composite morbidity. Multivariable analyses were stratified by parity and adjusted for clustering by site. 15,525 women met inclusion criteria: 10,421 with early AROM and 5,104 without. Table 1 displays study group characteristics. Early AROM was associated with a shorter time to vaginal delivery by 4.5hr for nulliparas and 1.3hr for multiparas (p<.001 for both). Labor duration remained significantly shorter in Cox proportional hazard regression (Table 2). After controlling for confounders in multivariable regression, early AROM was significantly associated with a 1.31-times higher odds of cesarean in nulliparas and 1.15-times higher odds of cesarean in multiparas. There were no increased odds of composite maternal or neonatal morbidity for nulliparas with early AROM, however, there was a 1.35-times higher odds of neonatal morbidity in multiparas with early AROM. Early AROM < 4cm appears to decrease the duration of labor induction, but may increase the odds of cesarean delivery. Early AROM is not associated with increased maternal or neonatal morbidity in nulliparous women, however, it may increase the odds of neonatal morbidity in multiparas.View Large Image Figure ViewerDownload Hi-res image Download (PPT)