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Recording available 2/16-5/2
Recording available 2/16-5/2
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Abstract Award
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Poster Session 4

Category: Labor

Poster Session 4

(1045) Development of an Updated Predictive Model for VBAC Success

Thursday, February 12, 2026
3:30 PM - 5:00 PM  

    Submitting Author(s)

  • Bryce T. Munter, MD (she/her/hers)

    Maternal Fetal Medicine Fellow
    Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, McGovern Medical School at UT Health Houston
    Houston, Texas, United States

    • Presenting Author(s)

  • Karla M. Martin, MD (she/her/hers)

    Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
    Houston, Texas, United States

    • Coauthor(s)

  • Irene A. Stafford, MD, MPH, MS

    Associate Professor
    Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
    Houston, Texas, United States

Objective:
The commonly used vaginal birth after cesarean (VBAC) calculator does not account for the specific subtype of labor dystocia that resulted in prior cesarean delivery (CD) or include patients with multiple prior CD. To address the impact of these factors on VBAC success rates, we aimed to develop a novel predictive model incorporating these previously unevaluated variables and compare them to the current VBAC calculator.

Study Design:
We performed a retrospective case-control study of all women who attempted trial of labor after cesarean (TOLAC) and delivered at a large county hospital system in Houston, TX from 1/2019-1/2022. Data were collected using ICD-10 codes and detailed chart review. Variables included maternal comorbidities, obstetric history, detailed reason for prior CD, and maternal and neonatal outcomes. A multivariate logistic ridge regression model using stepwise backward elimination identified predictors of successful VBAC with variables significant at P < 0.05. Results were expressed as odds ratios (OR) with 95% confidence intervals (CI) and compared to the OR used in the current MFMU VBAC calculator.

Results:
During the study period, 3,036 patients with prior cesarean delivered, of which 1160 (38%) attempted TOLAC. Among these, 393 (34%) ultimately underwent repeat CD, while 767 (66%) had successful VBAC. History of two prior CD did not decrease VBAC success odds compared to one prior CD (OR 1.1 (CI 0.66-1.75). Compared to patients who had initial CD for reasons other than labor dystocia, patients who had initial CD for active phase arrest had lowest chances of VBAC success (OR 0.02, 95% CI 0.02-0.03), followed by prior CD for failed induction ( < 6cm dilation, OR 0.03, 95% CI 0.02-0.03), then prior CD for arrest of descent (OR 0.1 (95% CI 0.04-0.18). Twenty patients had uterine rupture (1.7%). 

Conclusion:
These results indicate that prior labor dystocia details should be considered in VBAC prediction calculators.