FIRST-TRIMESTER MATERNAL SERUM CONCENTRATIONS OF FETAL ANTIGEN 2 IN NORMAL PREGNANCIES AND THOSE AFFECTED BY TRISOMY-21

Serum concentrations of fetal antigen 2 (FA-2), the amino-propeptide o f the al chain of collagen type I, were measured in peripheral blood f rom women with normal (n = 234) and trisomy 21 affected (n = 14) pregn ancies between 9 and 11 weeks gestation. Serum FA-2 concentrations wer e seen to be stable throughout this period, and though raised FA-2 con centrations were seen at the 10th week of gestation, a statistically s ignificant difference between normal and trisomy 21 affected pregnanci es was not found overall. Therefore it seems unlikely that FA-2 has a role in first trimester screening for trisomy 21, despite the fact tha t significantly higher FA-2 concentrations in trisomy 21 and significa ntly lower concentrations in trisomy 18 had been previously demonstrat ed in amniotic fluid in the second trimester.