In addition, since fetuin A, which is mainly a fetal protein [5], is a well-known negative acute-phase reactant whose levels decrease as a response to exogenous or endogenous stimuli [16], the reduced amount of fetuin A in the amniotic fluid derived from pregnancies with trisomy 21 may indicate important oxidative stress which can lead to various, as yet unknown, abnormal processes during this early-midfetal stage. The gene discussed is AHSG; the disease is trisomy 21.