The Association between Early Artificial Amniotomy and Chorioamnionitis in Nulliparous Induction of Labor

Objectives. To investigate whether early artificial amniotomy (AROM) <4 cm in nulliparous women admitted for induction of labor was associated with an increased rate of chorioamnionitis and cesarean section or a decreased time to vaginal delivery. Study Design. A retrospective cohort study was performed on nulliparous women with a term, singleton gestation and intact membranes who presented for induction of labor (January 2008 to December 2011). Chorioamnionitis was defined using ICD9 codes. Results. 1,567 women were enrolled; 25.4% underwent early AROM. Overall, the prevalence of chorioamnionitis was 12.4%, the rate of cesarean section was 32.2%, and the time from 4 cm cervical dilation to vaginal delivery was 413 min. Compared to women without AROM < 4 cm, early AROM did not affect overall chorioamnionitis rates (10.2 versus 13.2%, P = 0.12) but was associated with an increased cesarean section rate (40.2 versus 29.5%, P < 0.001). However, among those who delivered vaginally, AROM < 4 cm decreased the rate of chorioamnionitis (8.4 versus 14.6%, P = 0.01), which persisted when controlling for potential confounders (OR 0.55, 95% CI 0.33-0.92), and decreased the time from 4 cm dilation to vaginal delivery (329 versus 472 min, P < 0.001). Conclusions. Our findings do not suggest that early AROM is associated with an increased rate of clinical chorioamnionitis.