A Novel Dual Outcome Risk Score for VBAC Success and Neonatal Morbidity

Objective: To develop and externally validate a simple antepartum cumulative risk score that stratifies both vaginal birth after cesarean (VBAC) success and neonatal morbidity among patients undergoing trial of labor after cesarean (TOLAC). Methods: This retrospective cohort study was conducted in 2 stages: model development in a single tertiary care center in California (2019 to 2025) and external validation in the National Vital Statistics System natality files (2020 to 2024). The derivation cohort included 1,418 TOLAC attempts; the national validation cohort included 477,693 TOLAC attempts. A point-based score was constructed from routinely available antepartum characteristics associated with VBAC. VBAC success and neonatal intensive care unit (NICU) admission were evaluated across score levels in both cohorts, and model discrimination was assessed using area under the receiver operating characteristic curve (AUC). Results: In the derivation cohort, 1,087 of 1,418 patients (76.7%) achieved VBAC. The logistic regression model showed reasonable discrimination (AUC 0.70, 95% CI 0.67-0.73). VBAC success declined from 89.1% at a score of -1 to 37.8% at scores of 4 or higher, whereas NICU admission increased from 31.7 to 200.0 per 1,000. Uterine rupture occurred in 28 of 1,418 TOLAC attempts (1.97%) and was not predicted by antepartum characteristics. In the national cohort, VBAC success similarly declined from 90.5% to 44.8%, whereas NICU admission increased from 43.8 to 111.1 per 1,000 across the same score range. Conclusion: A simple antepartum risk score stratified both VBAC success and neonatal morbidity in single-center and national TOLAC cohorts, supporting its potential use in patient-centered counseling.