Screening for Congenital Abnormalities

Abstract

Improvements in nutrition, sanitation, housing, and medical care have been associated with reductions in infectious diseases of infancy, such as diarrhea, and, concomitantly, with a decline in infant mortality. Although deaths from congenital abnormalities have also decreased, the rate of their decline has not kept pace with the overall rate. Thus in the United States they have become the most frequent cause of infant death (58). For abnormalities detected in the newborn period, which comprise 3% of all births, about 8 per cent are due to single gene disorders, 6 to 12% to chromosome abnormalities, and less than 5% to viral infections of the mother (39,69). Little is known about underlying causes in the remainder; polygenic factors, environmental agents, and, probably the most common, genetic-environmental interactions, account for them. Congenital abnormalities also contribute substantially to childhood hospitalizations in several developed countries (17). One chromosome disorder, Down's syndrome, accounts for about 16 to 30% of all severe mental retardation, with other genetic and chromosome disorders contributing another 15 to 20% (58). Although the incidence of congenital abnormalities differs to some extent geographically (39), it seems likely that as any country develops, the proportion of infant mortality and childhood disability due to congenital abnormalities will increase.