Maternal Age and Elective Inductions of Labor in Nulliparous Patients: A Multicenter Cohort Study

We aimed to investigate whether advanced maternal age is associated with cesarean delivery in nulliparous individuals undergoing elective induction of labor (eIOL).

We queried a multicenter outpatient electronic medical record to perform a retrospective cohort study of nulliparous individuals undergoing eIOL between 39^0/7 and 40^6/7 weeks from January 2017 to June 2024. To investigate the relationship between age and eIOL, we created multiple study cohorts: (1) Age <35 years, (2) age 35-39 years, and (3) age ≥40 years. 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.

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 years, 35-39 years, and ≥40 years, respectively. We found an increased incidence of cesarean delivery with increasing age (25.8% for age <35 years, 41.1% for age 35-39 years, and 55.6% for age ≥40 years, p < 0.01). After adjusting for confounders including pre-pregnancy body mass index (BMI), diet-controlled gestational diabetes, and in vitro fertilization, and using age <35 years as the reference in a multivariable regression, this relationship remained consistent (age 35-39: adjusted odds ratio (OR) = 1.82 [95% confidence interval (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.

Our findings highlight an association between increasing maternal age and cesarean delivery among nulliparous individuals undergoing eIOL. Further studies should determine whether biologic or immunologic factors play a role or whether altered labor management may improve these outcomes.

· Among patients undergoing eIOL, increased age is associated with cesarean delivery.. · After adjusting for confounders in multivariable regression, age remained associated with cesarean delivery.. · Future studies are needed to determine the etiology of increased cesarean delivery with maternal age..