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

OBJECTIVE: Evaluate the association between spontaneous active labor duration utilizing contemporary labor curves and risk of adverse outcomes.

MATERIALS AND METHODS: 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).

RESULTS: 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).

CONCLUSION: 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.