ABNORMAL AMNIOTIC FETAL-ANTIGEN-2 CONCENTRATIONS IN TRISOMY-18 AND TRISOMY-21

Fetal antigen 2 (FA-2) is a human protein, first identified in amnioti c fluid, and shown to be identical to the aminopropeptide of the alpha (1) chain of collagen type I, It exists in several different size and charge forms, In the present study, FA-2 was measured in amniotic flui d using two different assays: a rocket line immunoelectrophoretic assa y which measured total FA-2, and a radioimmunoassay which was specific for the high molecular mass forms of FA-2, Both assays gave similar r esults, FA-2 concentrations were measured in amniotic fluid samples co llected from normal pregnancies at 10-23 weeks gestation; they were sh own to rise steeply from 10-14 weeks, peak at 17 weeks and then fall s lightly by 23 weeks. Comparison between amniotic fluid from normal pre gnancies and pregnancies affected by trisomy, showed significantly hig her FA-2 concentrations in trisomy 18.