Increased concentrations of prostate-specific antigen in maternal serum from pregnancies affected by fetal Down syndrome.

Down syndrome is one of the most common causes of mental retardation in the industrialized world. Prenatal serum screening to identify mothers at risk of carrying a fetus affected with Down syndrome is presently part of routine obstetrical care. Prostate-specific antigen (PSA) concentration was measured in stored second-trimester maternal serum samples from 19 pregnancies affected with fetal Down syndrome and in 95 samples from unaffected pregnancies, with each case matched to five controls for gestational age and duration of frozen sample storage. Concentrations of PSA in Down syndrome pregnancy were significantly higher (case median = 2.28 multiples of the median; P = 0.02) than in unaffected pregnancy. PSA concentrations were not significantly correlated with the current serum screening analytes, alpha-fetoprotein, unconjugated estriol, or human chorionic gonadotropin in either cases or controls. The increased maternal serum PSA concentrations in Down syndrome pregnancy and their relative independence from other markers suggest the possible utility of PSA as a prenatal screening marker for fetal Down syndrome.