Maternal Age and Elective Inductions of Labor in Nulliparous Patients: a multicenter cohort study.

OBJECTIVE We aimed to investigate whether advanced maternal age is associated with cesarean delivery in nulliparous individuals undergoing elective induction of labor. STUDY DESIGN We queried a multicenter outpatient electronic medical record to perform a retrospective cohort study of nulliparous individuals undergoing elective induction of labor between 39w0d to 40w6d from January 2017 to June 2024. To investigate the relationship between age and elective induction of labor, we created multiple study cohorts: 1) age <35, 2) age 35-39, and 3) age ≥ 40. We excluded pregnancies complicated by multifetal gestation, oligohydramnios, hypertensive disorders, diabetes requiring treatment, autoimmune disorders, or fetal growth restriction. The primary outcome was the rate of cesarean delivery and secondary outcomes included indication for cesarean delivery and adverse maternal and neonatal outcomes. RESULTS Of the 84,156 eligible individuals, 932 met our inclusion criteria with 728 (78.1%), 141 (15.1%), and 63 (6.8%) with age < 35, age 35-39, and age ≥ 40, respectively. We found an increased incidence of cesarean delivery with increasing age (25.8% for age<35, 41.1% for age 35-39, and 55.6% for age ≥ 40, p<0.01). After adjusting for confounders including pre-pregnancy BMI, diet-controlled gestational diabetes, and in vitro fertilization, and using age < 35 as the reference in a multivariable regression, this relationship remained consistent (age 35-39 adjusted OR 1.82 (95% CI 1.14-2.91) and age ≥ 40 adjusted OR 3.70 (95% CI 1.90-7.22)). Aside from cesarean for arrest of dilation, there were no significant differences noted in the indications for cesarean delivery or other adverse outcomes. CONCLUSION Our findings highlight an association between increasing maternal age and cesarean delivery among nulliparous individuals undergoing elective induction of labor. Further studies should determine whether biologic or immunologic factors play a role or whether altered labor management may improve these outcomes.