Objectives: to determine prognostic factors for vaginal delivery in pregnant women after previous cesarean section admitted to CAM-IMIP in labor.Patients and Methods: a case-control study was performed, analyzing all deliveries of patients with previous cesarean section admitted to CAM-IMIP between January 1991 and December 1994. Patients who had a cesarean section (n=156) were considered cases while patients with a vaginal birth were the controls (n=338). Inclusion criteria were: gestational age > 36 weeks, previous cesarean section at least 1 year before, alive fetus, spontaneous labor and vertex presentation. Patients with high-risk pregnancies, acute fetal distress and a previous vaginal delivery after cesarean section were excluded. Statistical analysis was performed with in Epi-Info 6.0 and Epi-Soft, using c² test, Fisher's exact test and Student's "t" test. Odds ratio and its 95% confidence interval was calculated and multiple logistic regression analysis was performed for the control of confounding factors. Results: overall rate of cesarean section was 31.6%. Maternal factors significantly associated with vaginal delivery were age < 20 years (OR = 2.07, 95% CI = 1.18-3.66) or > 35 years (OR = 0.54, 95% CI = 0.36-0.82), history of vaginal delivery (OR = 1.6, 95% CI = 1.01-2.55) and complications of pregnancy as indication for previous cesarean section (OR = 3.67, 95% CI =1.19-12.02). A significant association with vaginal delivery could not be detected for other variables: interval between previous cesarean section and present delivery, other indications for cesarean section and type of uterine suture. In a multiple logistic regression model the variables that remained associated with vaginal delivery were maternal age and previous vaginal delivery. Conclusions: maternal age below 20 years, previous cesarean section indicated due to gestational complications and previous vaginal delivery were favorably associated with vaginal delivery in patients with prior cesarean section. Risk of repeated cesarean section is increased in pregnant women aged 35 years or above. These factors should be contemplated when obstetrical evaluation of the delivery route is performed.
Cesarean section; Vaginal delivery; Operative delivery; Resolution of pregnancy