Prenatal diagnosis of inborn errors of metabolism.

More than 50 inborn errors of metabolism can be diagnosed in the fetus. This is accomplished by evaluation of constituents of the cell free amniotic fluid or of cultured or uncultured amniotic fluid cells. Only those syndromes with specific abnormal contributions to amniotic fluid can be so diagnosed. Currently diagnosable diseases and their assay methods are reviewed. Such assay methods must be able to differentiate the unaffected heterozygote from the affected homozygote.