Labor Dystocia in Nulliparous Women.

Dystocia (abnormally slow or protracted labor) accounts for 25% to 55% of primary cesarean deliveries. The latent phase of labor begins with onset of regular, painful contractions and continues until 6 cm of cervical dilation. Current recommendations are to avoid admission to labor and delivery during the latent phase, assuming maternal/fetal status is reassuring. The active phase begins at 6 cm. An arrested active phase is defined as more than four hours without cervical change despite rupture of membranes and adequate contractions and more than six hours of no cervical change without adequate contractions. Managing a protracted active phase includes oxytocin augmentation with or without amniotomy. The second stage of labor begins at complete cervical dilation and continues to delivery. This stage is considered protracted if it lasts three hours or more in nulliparous patients without an epidural or four hours or more in nulliparous patients with an epidural. Primary interventions for a protracted second stage include use of oxytocin and manual rotation if the fetus is in the occiput posterior position. When contractions or pushing is inadequate, vacuum or forceps delivery may be needed. Effective measures for preventing dystocia and subsequent cesarean delivery include avoiding admission during latent labor, providing cervical ripening agents for induction in patients with an unfavorable cervix, encouraging the use of continuous labor support (e.g., a doula), walking or upright positioning in the first stage, and not diagnosing failed induction during the latent phase until oxytocin has been given for 12 to 18 hours after membrane rupture. Elective induction at 39 weeks' gestation in low-risk nulliparous patients may reduce the risk of cesarean delivery.