Maternal age and risk of fetal death in singleton gestations: USA, 1995-2000

To determine the magnitude of risk for fetal death among singleton pregnancies in relation to maternal age, and to compare the risks with other common indications for fetal testing.

We performed a retrospective cohort analysis of singleton births delivered between 1995 and 2000 using the US linked birth/infant death data. Gestational age at < 24 weeks and fetuses with anomalies were excluded. Fetal death rates at > or = 24 and > or = 32 weeks were calculated among women aged 15-19, 20-24, 25-29, 30-34, 35-39, 40-44 and 45-49 years, as well as for other common indications for testing: chronic and pregnancy-induced hypertension, diabetes and small-for-gestational age (SGA). The association between maternal age and fetal deaths was derived after adjusting for potential confounders through multivariable logistic regression models. Relative risks (RR) and 95% confidence intervals (CI) were derived from these models after adjusting for the effects of gravidity, race, marital status, prenatal care, education, smoking and placental abruption.

Among the 21,610,873 singleton births delivered at > or = 24 weeks, fetal deaths occurred in 58,580 (2.7 per 1000). Births to young (15-19 years) and older (> or = 35 years) women comprised 12.6% and 11.4%, respectively. Compared with women aged 20-24 years, young women did not experience an increased risk of fetal death. However, increasing rates of fetal death at > or = 24 and at > or = 32 weeks were seen with increasing maternal age. The RR for fetal death at > or = 24 and at > or = 32 weeks among women 35-39 years were 1.21 and 1.31, respectively, while the RRs were 1.62 and 1.67 among women aged 40-44 years. Women 45-49 years were 2.40-fold (95% CI 1.77, 3.27) and 2.38-fold (95% CI 1.64, 3.46) as likely to deliver a stillborn fetus at > or = 24 weeks and > or = 32 weeks, respectively. RRs for fetal death at > or = 24 and > or = 32 weeks for hypertensive disease, diabetes, and SGA ranged between 1.46 and 4.95.

Fetal deaths are increased among older women (> or = 35 years). Fetal testing in women of advanced maternal age may be beneficial.