Objective: To determine the relationship between maternal age and labor induction duration among nulliparous women.
Methods: This retrospective cohort study included nulliparous women with non-anomalous, term, singleton pregnancies undergoing labor induction with intact membranes at a tertiary-care academic hospital from January 2015 to April 2017. Maternal age was stratified as follows: <25 years, 25-29 years, 30-34 years, 35-39 years, and ≥ 40 years. The primary outcome was induction duration, defined as the time the first induction agent was administered to time of birth. Secondary outcomes were cesarean delivery, cesarean indication, hemorrhage, blood transfusion, peripartum infection, composite neonatal morbidity, and induction duration among the subset of women who ultimately underwent cesarean. The data were analyzed using chi-squared and Fisher exact tests. Multivariable regression was used to adjust for maternal race/ethnicity, maternal body mass index, gestational age at start of induction, and induction indication. Hazard ratios were used to calculate induction duration among women who underwent cesarean delivery, stratified by age and adjusted by the same variables.
Results: Among the 955 patients included, the median induction duration was 32.3 h (interquartile range (IQR) 20.4-41.0 h). Women 40 years and older had a slight increase in induction duration (adjusted odds ratio (aOR) 1.03, 95% confidence interval (CI) 1.01-1.05) and a seven-fold increased risk of induction lasting 60 h or longer (adjusted relative risk (aRR) 7.3, CI 1.8-29.9) when compared to those under 25 years of age; otherwise, there was no association between maternal age and labor induction duration. There was no association between age and cesarean delivery, cesarean indication, hemorrhage, transfusion, peripartum infection, or adverse neonatal outcomes. Furthermore, there was no association between maternal age and induction duration even among women who ultimately underwent cesarean.
Conclusion: We found no association between maternal age and induction duration for women under 40 years of age. For women 40 years of age and older, these was an increased risk of labor induction lasting 60 h or longer. Despite this, we found no association between maternal age and cesarean delivery or other adverse maternal or fetal outcomes.
Keywords: Induction of labor; advanced maternal age; labor induction duration; maternal age; obstetrics; outcomes; perinatal outcomes; pregnancy; prolonged induction.