98: Second stage duration and labor outcomes in nulliparous women with neuraxial analgesia

Abstract

Optimal duration of the second stage should maximize the chance of spontaneous vaginal delivery while minimizing morbidity. We tested the hypothesis that increasing second stage duration is associated with decreased rates of spontaneous vaginal delivery and increased rates of maternal and neonatal morbidity. Planned secondary analysis of data from the Optimizing Management of the Second Stage (OMSS) multicenter randomized trial in which nulliparous women with term pregnancies and neuraxial analgesia were randomly assigned at complete cervical dilation to immediate pushing or delay for 1 hour. The primary outcome was spontaneous vaginal delivery. Secondary outcomes were cesarean, operative vaginal delivery, composite neonatal morbidity, severe perineal lacerations (3rd or 4th degree) and postpartum hemorrhage. Composite neonatal morbidity was defined as occurrence of one or more of: neonatal death, serious birth injury (skull fracture, brachial plexus injury, cephalohematoma), umbilical cord arterial acidosis, respiratory distress, transient tachypnea, meconium aspiration with pulmonary hypertension, hypoxic-ischemic encephalopathy, hypoglycemia, hypothermia treatment, or suspected neonatal sepsis. Multivariable logistic regression was used to estimate adjusted odds ratios for outcomes with each additional hour compared to the first hour. A total of 2404 patients were included; 1200 immediate and 1204 delayed pushing. Rate of spontaneous vaginal delivery was significantly lower beyond 2 hours, with a corresponding increase in operative vaginal delivery and cesarean (Table). Rates of the composite neonatal morbidity and severe perineal lacerations increased nearly 2- fold with second stage duration beyond 3 hours. Rate of postpartum hemorrhage was not significantly different with increasing second stage duration. Among nulliparous women with neuraxial analgesia at term, increased second stage duration is associated with lower rate of spontaneous vaginal delivery and increased rate of maternal and neonatal morbidity especially beyond 3 hours. These findings should inform decisions on acceptable duration of the second stage.