Fetal deaths in the United States. Influence of high-risk conditions and implications for management.

Objective: To estimate the effect of specific maternal-fetal high-risk conditions on the risk and timing of fetal death.

Methods: This study examined 10,614,679 non-anomalous singleton pregnancies delivering at or beyond 24 weeks' gestation, derived from the U.S. linked birth/infant death data sets, 1995-1997. Fetal death rates for pregnancies at low risk were compared with pregnancies complicated by chronic hypertension, gestational hypertensive disorders, diabetes, small for gestational age infants, and abruption. Adjusted relative risks as well as population-attributable risks for fetal death were derived by gestational age for each high-risk condition compared with low-risk pregnancies.

Results: The fetal death rate for low-risk pregnancies was 1.6 per 1000 births. Adjusted relative risk for fetal death was 9.2 (95% confidence interval [CI] 8.8, 9.7) for abruption, 7.0 (95% CI 6.8, 7.2) for small for gestational age infants, 1.4 (95% CI 1.3, 1.5) for gestational hypertensive disorders, 2.7 (95% CI 2.4, 3.0) for chronic hypertension, and 2.5 (95% CI 2.3, 2.7) for diabetes. Fetal death rates were lowest between 38 and 41 weeks. The fetal death rate (per 1000 births) for these high-risk conditions was 61.4, 9.6, 3.5, 7.6, and 3.9, respectively. Almost two thirds of fetal deaths were attributable to the pregnancy complications examined.

Conclusion: High-risk conditions in pregnancy are associated with an increased risk for fetal death, particularly in the third trimester. Delivery should be considered at 38 weeks, but no later than 41 weeks, for these pregnancies.