Maternal age and the risk of stillbirth throughout pregnancy in the United States.

ABSTRACT

OBJECTIVE: The objective of the study was to examine the relationship of maternal age with stillbirth risk throughout gestation. STUDY DESIGN: A total of 5,458,735 singleton gestations without reported congenital anomalies from the 2001 to 2002 National Center for Health Statistics perinatal mortality and natality files were analyzed. Hazard rates (risk) of stillbirth (fetal death 20 weeks or longer) were calculated for each week of gestation. RESULTS: The risk of stillbirth at 37 to 41 weeks for women 35 to 39 years old was 1 in 382 ongoing pregnancies and for women 40 years old or older, 1 in 267 ongoing pregnancies. Compared with women younger than 35 years old, the relative risk of stillbirth was 1.32 (95% confidence interval 1.22, 1.43) for women 35 to 39 years old and 1.88 (95% confidence interval 1.64, 2.16) for women 40 years old or older at 37 to 41 weeks. This effect of maternal age persisted despite accounting for medical disease, parity, and race/ethnicity. CONCLUSION: Women who are of advanced maternal age are at higher risk of stillbirth throughout gestation; the peak risk period is 37 to 41 weeks.