Duration of Spontaneous Active Labor and Perinatal Outcomes Using Contemporary Labor Curves

Abstract

Evaluate the association between spontaneous active labor duration utilizing contemporary labor curves and risk of adverse outcomes. This is a retrospective cohort study from January 2012 to January 2015. Subjects were nulliparous, 18 to 44 years, with a cephalic, singleton ≥37 weeks in spontaneous labor. Subjects were placed into three subgroups, defined by active labor duration from 6 to 10 cm as less than the median, the median-95th, and >95th percentile based on contemporary labor curves published by Zhang et al. We evaluated the association between subgroups and cesarean delivery, chorioamnionitis, estimated blood loss, Apgar score < 7 at 5 minutes, and neonatal intensive care unit admission using logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). Six-hundred forty two women met the inclusion criteria. Compared with women whose active labor was less than the median, the risk of cesarean was higher in the median-95th percentile ([adjusted OR, aOR] 3.1, 95% CI 1.8-5.5) and the >95th percentile ([aOR] 6.8, 95% CI 3.9-11.7) subgroups. There was an increased odds of chorioamnionitis in the median-95th percentile subgroup ([aOR] 2.5, 95% CI 1.1-5.9). Chorioamnionitis and cesarean delivery increased significantly as labor duration exceeded the median. This study provides a better understanding regarding the potential risk of cesarean and chorioamnionitis using contemporary labor curves.