Trial of labor after previous cesarean section: prognostic indicators of outcome.

A cross-sectional analytic survey of 92 patients permitted to attempt vaginal delivery after previous lower segment cesarean section ("trial of scar") is reported. Variables which may predict mode of delivery were assessed. Fifty patients (54.3%) were delivered vaginally; 42 patients (45.7%) had repeat cesarean sections in labor. There were three cases of scar dehiscence (3.2%). There were no maternal or fetal mortality. When the cervix was less than 3 cm dilated at initial examination in labor, 10 of 37 patients (27%) were delivered vaginally, compared to 38 of 55 patients (69%) who were delivered vaginally when the cervix was greater than 3 cm dilated. Assessment of cervical dilatation on admission in labor proved to be the most significant prognostic factor at the onset of labor, with regard to successful vaginal delivery in a patient with a lower segment cesarean section scar.