586: Do the “right” candidates for vaginal birth after cesarean delivery choose a trial of labor?

Abstract

The Maternal Fetal Medicine Units Network (MFMU) vaginal birth after cesarean delivery (VBAC) predictive model is widely used to inform counseling. We sought to evaluate the association between predicted chance of successful VBAC and attempted trial of labor after cesarean (TOLAC) and to identify other factors associated with TOLAC. This is a single-center retrospective cohort study of term singleton births in 2010 to women with one prior cesarean. Women with contraindications to VBAC or missing data to calculate predicted chance of successful VBAC (VBAC score) were excluded. VBAC score was calculated using the MFMU VBAC predictive model. Patients were stratified into 3 groups based on VBAC score: low (VBAC score <50%), moderate (VBAC score 50-69.9%) and high (VBAC score ≥70%). The association between TOLAC and predicted chance of success was interrogated with multivariable logistic regression. 764 births met inclusion criteria. The overall TOLAC rate was 37.7% (n=288) and 53.1% had a successful VBAC. The proportion of women with high, moderate and low VBAC scores was 39.7% (n=303), 46.1% (n=352), and 14.3% (n=109) respectively. Among women with a high score, 50.8% attempted TOLAC, compared to 29.8% and 26.6% of women with moderate and low scores. The odds ratio for TOLAC was 2.9 (CI: 1.9, 4.6, p<0.001) in women with high scores compared to low scores. There was no difference between women with moderate scores versus low scores (OR= 1.2 CI: 0.7, 1.9; p=0.5). Non-white women had lower VBAC scores than white women (median 60.6, IQR 46.7-73.0 vs median 66.7, IQR 57.4-76.4, p<.001), but were more likely to attempt TOLAC (51.8% vs 34.0%, p<.001). When stratified by predicted chance of success, non-white women were more likely than white women to attempt TOLAC in the moderate and high score groups. This remained significant when controlling for prior vaginal delivery, indication for prior cesarean and type of care provider with an adjusted OR of 3.4 (CI: 1.2,10.9, p=0.04) among women with a high score and 2.5 (CI: 1.2, 4.9, p=0.009) among women with a moderate score. Half of women with a high predicted rate of successful VBAC opt out of TOLAC, while almost a third of women with a low chance of successful VBAC opt for TOLAC. Race is strongly associated with attempted TOLAC in women with moderate and high predicted success.