[Predictive factors of the delivery method in women with cesarean section scars]. 
To determine the independent effect of clinical and non clinical factors on the mode of delivery after previous cesarean section.  We performed a retrospective multicenter study of 579 women who had previously undergone a cesarean section and who delivered between January 1995 and June 1997.  Maternal and perinatal morbidity associated with trial of labor and elective repeat cesarean was assessed.  Multiple logistic regression was used to identify prognostic factors for the outcome of a trial of labor.  The odds ratios provided indicate the risk of cesarean section when the factor is present.  The rate of successful trial of labor was 74.5%.  Overall morbidity was not increased in the trial of labor group.  The variables of significant predictive value were the Bishop's score (OR = 15.2 for a score < 3; 95% CI: 5.54 to 41.9), an anomaly of the pelvis (OR = 5.89; 95% CI: 2.37 to 14.7), a previous vaginal delivery (OR = 0.27; 95% CI: 0.12 to 0.60), a fetal distress (OR = 4.11; 95% CI: 2.01 to 8.43), the weight gain during pregnancy (OR = 2.01; 95% CI: 1.10 to 3.68), a delivery between 11 p.m. and 7 a.m. (OR = 0.29; 95% CI: 0.13 to 0.66), a hypertension (OR = 3.10; 95% CI: 1.09 to 8.80) and the use of an intra-uterine pressure catheter (OR = 0.26; 95% CI: 0.11 to 0.57).  A trial of labor should be allowed in most of the women with previous cesarean section.  The Bishop's score is the best predictor of the mode of delivery.  Induction of labor and a first cesarean for dystocia do not affect the chances of vaginal birth.