Evaluation of prognostic factors for vaginal delivery after cesarean section

Although the success rate of vaginal birth after cesarean section in selected patients is > 60%, most of these women elect the option of a planned repeat cesarean section. In this study our purpose was to evaluate the predictive value and relative importance of 15 prognostic factors by using univariate and multivariate analysis in order to refine the selection of patients for a trial of labor. The analyses were based on 261 patients with one prior cesarean section who were allowed a trial of labor. The final model resulted in six significant prognostic factors. The overall predictive value of the model was 68%. However, the predictive value for a successful vaginal delivery was excellent: 94.5% (139/147) of the women predicted to deliver vaginally actually did so. This group constituted 56% (147/261) of our candidates for vaginal delivery. The predictive value of the test for failure was only 33.3% (38/114); 66.6% of the women completed a vaginal delivery despite the prediction of failure. Because the chance of a successful vaginal delivery is > 60% in women with a prediction of failure, until a selection criterion with a better prognostic value can be identified, a liberal approach to vaginal birth after cesarean section is justified even in this group. A 60% chance is perceived by many women and physicians as too low to elect this option. Since we were able to predict a successful vaginal delivery in a large proportion of the candidates, it may encourage at least this group of patients to elect a trial of labor.