A single chorionic gonadotropin assay for maternal serum screening for Down's syndrome.

A simple enzyme immunoassay measuring human chorionic gonadotropin in undiluted maternal serum has been developed in order to be used as a prenatal screening test for Down's syndrome. A retrospective study of maternal serum sampled during pregnancies associated with trisomy 21 shows that with a 5% amniocentesis rate determined on a single test, the detection rate of trisomy 21 would be around two-thirds of the affected pregnancies. A prospective study of 9040 pregnant women under 38 years has confirmed the usefulness of the assay.