Vaginal birth after cesarean: Does accuracy of predicted success change from prenatal intake to admission?

Abstract

There are 2 prediction nomograms for vaginal birth after cesarean delivery. The first is based on variables that are available at the first prenatal visit, and the second includes variables at the time of admission. The purpose of this study was to compare the accuracy of prediction scores that are calculated by the intake and admission prediction nomograms in a modern cohort of racially and ethnically diverse women. This is a retrospective cohort study that analyzed the data for women with at least 1 previous cesarean delivery who attempted a trial of labor from 2007-2016 at a tertiary medical center. Participants were stratified into 3 probability-of-success groups: low (<35%), moderate (35-65%), and high (>65%). The primary outcome was the difference between the intake- and admission-predicted success scores in the 3 groups. Secondary outcomes were characteristics that were associated with successful vaginal birth after cesarean delivery . Of the 614 women included in the analysis, 444 (72.3%) had a successful vaginal birth after cesarean delivery . Predicted vaginal birth after cesarean delivery success rate ranged from 14.4-96.2%. Patients were stratified into 3 groups by intake predicted success rates: low (<35%; n=21), moderate (35-65%; n=136), and high (>65%; n=457). The change in predicted success rates was compared between the intake and admission nomograms. Women in the low and moderate groups improved their prediction score by approximately 7-8% when variables at the time of admission were included. As a result, more than one-half of these women (172/307; 56%) shifted to a higher predicted success group. The admission nomogram, as compared with the intake nomogram, more accurately predicted vaginal birth after cesarean delivery success in all groups. Analysis of admission variables showed that cervical dilation >2 cm compared with a closed cervix was the strongest predictor of successful vaginal birth after cesarean delivery (relative risk, 1.79; 95% confidence interval, 1.11-2.89). The admission prediction nomogram was more accurate and showed higher predicted success compared with the intake nomogram for the same cohort. Because prediction scores may improve at the time of admission, additional counseling on the risks and benefits of trial of labor may be helpful at that time.