AHSG and trisomy 21: We hypothesized that levels of fetuin A in amniotic fluid might differ between pregnancies with DS and euploid pregnancies and that presence or absence of features in the DS group may potentially be associated with the metabolic actions of fetuin A. Fetuin A, which has been studied in maternal serum as a potential novel marker in prenatal diagnosis of trisomy 21 in the first trimester, has not been found to differ significantly in levels between euploid and aneuploid pregnancies [10].