title: Validation of a Prediction Model for Vaginal Birth after Cesarean Delivery Reveals Unexpected Success in a Diverse American Population.
abstract: ObjectiveTo investigate the validity of a prediction model for success of vaginal birth after cesarean delivery (VBAC) in an ethnically diverse population.MethodsWe performed a retrospective cohort study of women admitted at a single academic institution for a trial of labor after cesarean from May 2007 to January 2015. Individual predicted success rates were calculated using the Maternal-Fetal Medicine Units Network prediction model. Participants were stratified into three probability-of-success groups: low (<35%), moderate (35-65%), and high (>65%). The actual versus predicted success rates were compared.ResultsIn total, 568 women met inclusion criteria. Successful VBAC occurred in 402 (71%), compared with a predicted success rate of 66% (p= 0.016). Actual VBAC success rates were higher than predicted by the model in the low (57 vs. 29%;p< 0.001) and moderate (61 vs. 52%;p= 0.003) groups. In the high probability group, the observed and predicted VBAC rates were the same (79%).ConclusionWhen the predicted success rate was above 65%, the model was highly accurate. In contrast, for women with predicted success rates <35%, actual VBAC rates were nearly twofold higher in our population, suggesting that they should not be discouraged by a low prediction score.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, California; Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California.
authors.forename: Melanie Mai
authors.initials: MM
authors.lastname: Maykin
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, California; Department of Maternal-Fetal Medicine, Obstetrix Medical Group of Houston, Shenandoah, Texas.
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Mularz
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, California.
authors.forename: Lydia K
authors.initials: LK
authors.lastname: Lee
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California, Los Angeles, California; Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco, California.
authors.forename: Stephanie Gaw
authors.initials: SG
authors.lastname: Valderramos
keywords: MFMU VBAC calculator; VBAC success; trial of labor after cesarean; vaginal birth after cesarean