They have been found to be elevated in amniotic fluid of pregnancies in which fetuses are affected by glutaric aciduria type II, a genetic disorder that can lead to brain malformations, enlarged liver, and other developmental problems.28 Glutaric aciduria type II can result from deficiencies in one of three proteins, the alpha (ETFA) and beta (ETFB) subunits of electron transfer flavoprotein, and electron transfer flavoprotein dehydrogenase (ETFDH).29 It is not known if Trisomy 21 may affect the expression of one or more of these functionalities. Here, ETFB is linked to multiple acyl-CoA dehydrogenase deficiency.