Predicting factors for success of vaginal delivery in preterm induction with prostaglandin E2
OBJECTIVE To determine the effects of labor induction with vaginal prostaglandin E2 (PGE2) on mode of delivery in post-term pregnancies and to identify possible predictors of successful vaginal delivery. METHODS The study group consisted of 211 women with post-term pregnancy (gestational age more than a full 41 weeks) admitted for induction of labor with vaginal applications of PGE2. Findings were compared with women with spontaneous onset of labor (group 2, n = 510). Women with previous Cesarean section were excluded from both study and control groups. RESULTS The rate of Cesarean section was significantly higher in the study group (19.4%) than in the control group (9%). A logistic regression model was used to control for maternal and gestational age, gravidity, parity, nulliparity rate, number of used PGE2 tablets, oligohydramnios and delivery weight as possible predictors of Cesarean section (R2 = 0.56, p < 0.001). On stepwise analysis, nulliparity (OR 45.2, 95% CI 2.93-695.5), number of PGE2 applications (OR 2.79, 95% CI 1.04-7.52) and maternal age (OR 1.23, 95% CI 1.01-1.50) were independently and significantly associated with increased risk of Cesarean section. PGE2 induction was a significant independent predictor of Cesarean section (OR 2.3, 95% CI 1.3-3.9). CONCLUSION PGE2 induction of labor was successful in approximately 80% of patients with post-term pregnancy, with apparently no serious maternal or fetal complications. Risk factors intrinsic to the patient, and labor induction itself, were the reasons for excess Cesarean deliveries in women with prolonged pregnancies.