Elevated maternal serum alpha-fetoprotein concentration and fetal chromosomal abnormalities.

Amniocentesis was performed in 1038 patients with elevated maternal serum alpha-fetoprotein (MSAFP) concentrations. Patients were divided into two groups based upon the amniotic fluid AFP concentration. Group 1 (N = 964) had a normal amniotic fluid AFP concentration and group 2 (N = 74) had elevated amniotic fluid AFP. Fetal chromosomal results were reviewed from the study population, with the finding of eight major fetal chromosomal abnormalities. Of the eight fetal chromosomal abnormalities, five were associated with elevated amniotic fluid AFP and three were associated with normal amniotic fluid AFP. The sensitivity and specificity of elevated amniotic fluid AFP concentrations in screening for a fetal chromosomal abnormality were 62.5 and 93.3%, respectively. In women with elevated MSAFP but normal amniotic fluid AFP concentrations, the probability of a major fetal chromosomal abnormality is extremely small.