Abstract
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.
Keywords
spontaneous labor - active labor duration - adverse perinatal outcomes - cesarean
delivery - chorioamnionitis
