Pregnancy at late premenopausal age: outcome of pregnancies at 45 years and older in Flanders, Belgium.

To describe the obstetric outcome in women at ages ≥ 45. A retrospective cohort study on a large existing database covering all deliveries in the Flanders region, Belgium, was performed, comparing obstetric outcomes at age 25, 35, 40 and 45 or older, for the period 2005-2010. In the period studied, 421 women gave birth at maternal age ≥ 45 vs 3,405, 15,206, 22,586 at ages 40, 35 and 25, respectively. With advancing maternal age, a significant linear increase for low birth weight (< 2,500 g) and preterm delivery (< 37, < 35 weeks and < 29 weeks), maternal hypertension and diabetes, both primary and secondary caesarean section, was noted. Between ages 40 and ≥ 45, both fetal and early neonatal death demonstrated a significant rise from 4.9/1,000 and 1.8/1,000 to 26/1,000 and 9.5/1,000, respectively. With advancing maternal age, a gradual but not statistically significant decline in the proportion of male fetuses was noted, from 51.6% at 25, to 47.2% in the oldest group. Multivariate analysis confirmed advanced maternal age to be a significant factor in low birth weight, preterm delivery, hypertension, diabetes, caesarean section and perinatal mortality. In Flanders, mothers at age 45 and older have a significantly increased risk for low birth weight, preterm delivery, hypertension, diabetes, caesarean section and perinatal mortality.