Diagnostic amniocentesis for the prenatal detection of genetic disorders has been shown to be useful to the physician in monitoring high risk pregnancies.1 The paper by Schneck, et al.2 in this issue of Pediatrics demonstrates not only the effective use of this technique for clinical management of the high-risk patient but documents its potential value for the study of the early stages of human metabolic disease. The presence of biochemical and structural alterations in cells and organs of fetuses affected with inborn errors of metabolism appears to be a common finding. Early gestational manifestations arising from the basic genetic defect have been found in Tay-Sachs disease,2-4 Niemann-Pick disease,5 Gaucher's disease,6 Pompe's disease,7 and Krabbe's disease.8