Predictors of Vaginal Birth at the Time of Admission in a Contemporary Cohort of Term Nulliparas

BackgroundDesigning a model to accurately predict vaginal birth in nulliparas may play a role in reducing cesarean delivery rates. This study aimed to identify predictors of vaginal birth at the time of admission in a contemporary and diverse cohort of nulliparous patients in the United States, and to assess the accuracy of the developed model. MethodsThis was a retrospective cohort study from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be. The present analysis included nulliparous patients with live, singleton, non-anomalous, term gestations, and no contraindications to vaginal birth. Candidate predictors were selected based on clinical knowledge and literature review. Bivariable analyses and multivariable logistic regression were used to establish factors independently associated with vaginal birth. A receiver operating characteristic curve was generated, and the area under the curve was calculated to estimate the predictive capacity of the final model. ResultsAmong the 6,043 individuals included, 5,058 (83.7%) delivered vaginally and 985 (16.3%) delivered via cesarean. Independent predictors of vaginal birth included maternal age, maternal height, body mass index at delivery, gestational age at delivery, group B Streptococcus status, chorioamnionitis, gestational hypertension/preeclampsia, diabetes, cervical dilation, cervical effacement, and fetal sex. The final predictive model achieved an area under the receiver operating characteristic curve of 0.79 (95% confidence interval, 0.77-0.81). ConclusionSeveral factors, most available prior to labor, were identified to be independently associated with vaginal birth at the time of admission among term nulliparous patients. Combining these independent predictors resulted in a clinical prediction model with fair predictive capability.