Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes.

OBJECTIVE The purpose of this study was to assess maternal and perinatal outcomes as a function of second-stage labor duration. STUDY DESIGN We assessed outcomes in nulliparous laboring women who were enrolled in a trial of fetal pulse oximetry. RESULTS Of 5341 participants, 4126 women reached the second stage of labor. As the duration of the second stage increased, spontaneous vaginal delivery rates declined, from 85% when the duration was <1 hour to 9% when it was > or =5 hours. Adverse maternal outcomes that were associated significantly with the duration of the second stage of labor included chorioamnionitis (overall rate, 3.9%), third- or fourth-degree perineal laceration (overall rate, 8.7%), and uterine atony (overall rate, 3.9%). Odds ratios for each additional hour of the second stage of labor ranged from 1.3-1.8. Among individual adverse neonatal outcomes, only admission to a neonatal intensive care unit was associated significantly with second stage duration (odds ratio, 1.4). CONCLUSION The second stage of labor does not need to be terminated for duration alone.