ADVANCES in biochemistry are helping scientists identify pregnant women who are at high risk for carrying a fetus with Down's syndrome.
Scientists now recognize three substances in the mother's serum—human chorionic gonadotropin, unconjugated estriol, and α-fetoprotein (AFP)—the concentrations of which, when coupled with the woman's age-associated risk, allow a more accurate calculation of the likelihood that she is carrying an affected fetus.
The prenatal blood test, administered during the second trimester and followed by amniocentesis and chromosome analysis on those mothers who are at risk, detects about 67% of all affected fetuses in the general pregnant population—a twofold to threefold improvement from the standard screening method that employs only AFP serum levels and age-associated risk.
Identifying Younger Patients
The new method helps to identify younger patients who are at high risk and should have amniocentesis performed but may not be offered the procedure under standard screening methods. It can also