Second trimester maternal serum alpha-fetoprotein as an indicator of fetal risk.

Serum alpha-fetoprotein levels were raised to 2.0 or more times the median for gestation in 30 of 507 singleton pregnancies after excluding pregnancies complicated by fetal neural tube defects. The serum alpha-fetoprotein levels were significantly more often elevated in pregnancies complicated by prematurity, fetal heart rate abnormalities, delivery of a small for dates infant, a perinatal death and admission of the baby to the neonatal unit. While the predictive value of an elevated serum alpha-fetoprotein was 76% for abnormal outcomes in general it ranged between only 16% and 46% for specific abnormalities. The usefulness of this assay relates only to its ability to predict an abnormal outcome when performed during the second trimester.