Objective.To identify factors predicting failure of cervical ripening with prostaglandin E2 (PGE2). Study design.A retrospective, cohort study of all women admitted for preinduction cervical ripening and failed to respond to PGE2 in comparison with randomly selected control group of women who underwent successful preinduction cervical ripening with PGE2 in a 3:1 ratio. Results.Overall 488 women were included, of them, 122 in the study group and 366 in the control group. A comparison between the two groups has revealed that maternal age above 30 years (OR2.7, 95-CI 1.35.6), nulliparity (OR4.1, 95-CI 1.710.0), prepregnancy BMI above 25kg/m2 (OR3.5, 95-CI 1.77.1), cervical dilatation of 1cm (OR9.1, 95-CI 3.513.4), cervical effacement of 50 or less admission (OR5.0, 95-CI 2.28.8), and gestational age of 37 weeks or less (OR2.9, 95-CI 1.36.6), are independent and significant predictors of cervical ripening failure with PGE2, and account for almost 50 of the variation in ripening outcome (R20.47). No association was found between the risk of cervical ripening failure and the indication for ripening, rupture of membranes, weight gain during pregnancy, weight before labor, diabetes or preeclampsia during pregnancy, and the newborn weight. Conclusions. Characterization of women who have a high probability for cervical ripening failure with PGE2 will help to improve consultation and may help choosing the optimal method for labor induction in these cases.