Pushing the bounds of second stage in term nulliparas with a predictive model

Background: Management of the second stage of labor continues to be a clinical challenge with unclear indications for abandoning attempts at spontaneous vaginal delivery. The conflict between diminishing chances of spontaneous vaginal delivery and increasing maternal and neonatal morbidity is difficult to quantify, leading to significant variation in management between providers, and variation in rates of operative vaginal delivery and cesarean birth. Objective: The objective of the study was to develop an hourly prediction model for spontaneous vaginal delivery during the second stage of labor in nulliparous women with epidural anesthesia. Study Design: This was a secondary analysis of the Consortium for Safe Labor database. The Consortium for Safe Labor collected data from 228,652 patients at 19 hospitals in the United State from 2002 through 2008. Primary outcome was delivery type per hour of second stage: spontaneous vaginal delivery vs operative delivery (operative vaginal and cesarean delivery). Inclusion criteria were term nulliparas with singleton gestations, vertex presentation, and attainment of 10 cm cervical dilation with epidural anesthesia. Exclusion criteria were intrauterine fetal demise, planned cesarean delivery, and major congenital anomalies. An optimal decision tree was used to create a prediction model. A test set was withheld from the data set to perform validation. A risk calculator tool was developed for prediction of spontaneous vaginal birth as well as adverse perinatal outcomes per hour. Adverse maternal outcomes were a composite of postpartum hemorrhage, transfusion, endometritis and third-/fourth-degree laceration. Adverse neonatal outcomes were a composite of neonatal intensive care unit admission, hypoxic ischemic encephalopathy, respiratory distress, seizures, apnea, asphyxia, and shoulder dystocia. Results: The study population included 228,438 deliveries; 26,796 patients met inclusion and exclusion criteria. After removing cases with incomplete data, the study population consisted of 22,299 women, of which 16,593 women had a spontaneous vaginal delivery (74.4%). The number of deliveries at a given hospital per year, fetal position, cervical dilation on admission, chorioamnionitis, augmentation of labor, maternal age, and length of second stage were associated with the odds of spontaneous vaginal delivery. Using the predictors identified, a risk predictor calculator was created, taking into consideration the length of time in the second stage. A receiver-operator characteristic curve was developed to assess the calculator; area under the curve was 0.73. This calculator is available at https://www.pushprescriber.com/. Conclusion: Spontaneous vaginal delivery for women with term, cephalic, singleton gestations with epidural anesthesia was associated with several variables. This calculator tool helps facilitate provider decision making and patient counseling about the value of continuing the second stage of labor based on changing rates of success and risks of maternal and neonatal morbidity with time.