Primary cesarean section and adverse delivery outcomes among women of very advanced maternal age

To assess associations between primary cesarean delivery and adverse delivery outcomes with very advanced maternal age.

We conducted a population-based cohort study including 78,880 births to mothers 25 years and older with singleton births from 2003 to 2012 using Washington State birth certificates and hospital discharge data, excluding births to women with a prior cesarean section. The primary outcome was mode of delivery. Secondary outcomes included maternal transfusion, chorioamnionitis, severe perineal lacerations and prolonged length of stay. Outcomes of births to women of advanced maternal age (35 to 39, 40 to 44) and very advanced maternal age (45 to 49, ⩾50) were compared with referent births among women aged 25 to 34 years. General linear models with a log-link function were used to calculate unadjusted and adjusted relative risks and 95% confidence intervals (CIs).

Proportions and risks of primary cesarean section increased with age (25 to 34 years, referent: 20.0%; 35 to 39 years: 25.9%, relative risk (RR)=1.25 (95% CI=1.20 to 1.29); 40 to 44 years: 30.9%, RR=1.45 (95% CI=1.40 to 1.50); 45 to 49 years: 35.7%, RR=1.59 (95% CI=1.45 to 1.75); and ⩾50 years: 60.7%, RR=2.44 (95% CI=1.95 to 3.05); P-trend <0.001). Associations did not differ between primiparous and multiparous women. No differences were noted for measures of maternal morbidity, except there was a trend of increasing risk of prolonged length of stay among births to older women (P-trend <0.001).

Primary cesarean delivery risk continues to increase above age 35 regardless of prior vaginal birth, with the highest risk among women aged 50 years and older.