Predictors of Failed Induction of Labor in Term Pregnancies: A Prospective Observational Study

Abstract

Background: Induction of labor (IOL) is a commonly performed obstetric intervention when continuation of pregnancy poses greater maternal or fetal risk than delivery. However, induction does not always result in successful vaginal delivery, and failed induction may contribute to increased operative delivery. Identification of factors associated with failed induction can facilitate appropriate counseling and individualized management. Objective: The objective of the study was to identify predictors of failed IOL among women with term pregnancies and evaluate their association with maternal and neonatal outcomes. Methods: A prospective observational study was conducted in the Department of Obstetrics and Gynaecology at a tertiary care teaching hospital. Sixty women with singleton term pregnancies (37+0–41+6 weeks) undergoing IOL were consecutively enrolled after informed consent. Maternal characteristics, parity, body mass index (BMI), gestational age, indication for induction, estimated fetal weight and pre-induction Bishop score were recorded. Details of induction methods and intrapartum outcomes were documented prospectively. The primary outcome was failed IOL, defined according to the study protocol as failure to achieve successful labor and vaginal delivery despite adequate cervical ripening and an adequate trial of induction. Associations between potential predictors and induction outcome were assessed using appropriate statistical tests, with P < 0.05 considered statistically significant. Results: Successful induction occurred in 48 (80.0%) women, while 12 (20.0%) experienced failed induction. Failure was more frequent among primigravidas than multigravidas (29.4% vs. 7.7%) and increased with maternal BMI, from 8.0% in women with BMI <25 kg/m2–45.5% in those with BMI ≥30 kg/m2. Women with gestational age >40 weeks and estimated fetal weight >3.5 kg also had higher failure proportions. Bishop score showed the strongest association with outcome (P < 0.001); failure occurred in 50.0% of women with Bishop score ≤3 compared with none among women with score ≥8. Conclusion: An unfavorable Bishop score was the strongest factor associated with failed induction. Primiparity, higher BMI, advanced gestation and higher estimated fetal weight also showed an association with induction failure. Comprehensive pre-induction assessment may improve counseling and clinical decision-making.