Prospective risk of stillbirth.

Some fraction of any cohort of fetuses alive at a given gestational age will ultimately die before birth. The residual prospective risk of stillbirth as a function of gestational age was calculated from records of the New York City Department of Health covering 370,051 reported births between 1987-1989, including 2454 stillbirths. In the general population, the prospective risk of stillbirth at 26 weeks was one in 150 and, because the time distributions of live births and stillbirths were not proportionate, the risk changed with gestational age. By 40 weeks' gestation, it was one in 475, rising progressively thereafter to one in 375 at 43 weeks. The prospective risk of stillbirth was elevated in certain ethnic groups and increased significantly with advanced maternal age, multiple gestation, and lack of prenatal care. The prospective risk of stillbirth is an important consideration in decisions regarding timing of delivery.