Objective: To identify independent risk factors for cesarean delivery after induction of labor and to develop a nomogram for predicting cesarean delivery among nulliparous women undergoing induction of labor at term.
Methods: This is a retrospective cohort study including nulliparous women with singleton, term (37 0/7 weeks of gestation or greater), cephalic pregnancies undergoing induction of labor from July 1, 2006, through May 31, 2012, at a tertiary care academic center. Inductions were identified using International Classification of Diseases, 9th Revision codes. Demographic, delivery, and outcome data were abstracted manually from the medical record. Women with a contraindication to vaginal delivery (malpresentation, abnormal placentation, prior myomectomy) were excluded. Independent risk factors for cesarean delivery were identified using logistic regression.
Results: During the study period, there were 785 nulliparous inductions that met study criteria; 231 (29.4%) underwent cesarean delivery. Independent risk factors associated with an increased risk of cesarean delivery included older maternal age, shorter maternal height, greater body mass index, greater weight gain during pregnancy, older gestational age, hypertension, diabetes mellitus, and initial cervical dilation less than 3 cm. A nomogram was constructed based on the final model with a bias-corrected c-index of 0.709 (95% confidence interval 0.671-0.750).
Conclusion: We identified independent risk factors that can be used to predict cesarean delivery among nulliparous women undergoing induction of labor at term. If validated in other populations, the nomogram could be useful for individualized counseling of women with a combination of identifiable antepartum risk factors.
Level of evidence: II.