Maternal Age and Risk of Fetal Death in Singleton Gestations: United States, 1995???2000

Abstract

Women less than 20 or more than 35 years of age account for at least one fourth of all births in the United States today. Advancing maternal age could increase the risk of fetal death, warranting antenatal testing. The risk of fetal death was examined retrospectively in a cohort of 21,610,873 singleton births taking place at or after 24 weeks gestation. The investigators analyzed U.S. perinatal mortality data on linked birth-infant deaths in the years 1995 to 2000. Eligible births numbered 21,610,873. Women less than 20 years of age and those aged 35 and older made up 12.6% and 11.4% of all births, respectively. Proportions of primigravid women, blacks, unmarried subjects, and smokers declined as maternal age increased. The overall rate of fetal death at and after 24 weeks gestation was 2.7 per 1000 total births. The lowest rates of fetal death were in women aged 25–29 and 30–34 years (2.4 per 1000 births). The adjusted relative risk of fetal death was not increased in young women, but did increase progressively for women aged 35–39 and 40–44 years, reaching 2.4 in women 45–49 years of age. The association of age with fetal death was noted in both blacks and whites but, at ages 45–49 years, was stronger for blacks. Relative risk values were 2.4% for chronic hypertension, 1.5% for pregnancy-induced hypertension, 1.9 for diabetes, and 4.4 for small-for-gestational age cases. The overall rate of fetal death at and after 32 weeks gestation was 1.9 per 1000 total births. The rate was lowest at ages 25–29 and 30–34 years (1.7 per 1000). These findings affirm that advanced maternal age independently increases the risk of fetal death and suggests that advanced maternal age alone could be a valid reason for antenatal fetal testing. It is not yet clear, however, whether the degree of increased risk is great enough to warrant testing.