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August 14, 1981

Down's Syndrome: Recent Trends in the United States

Author Affiliations

From the US Department of Health and Human Resources, Public Health Service, Centers for Disease Control, Bureau of Epidemiology, Atlanta.

JAMA. 1981;246(7):758-760. doi:10.1001/jama.1981.03320070042022

The crude incidence of Down's syndrome (DS) in the United States is currently about 1/1,000 births. Reduction in the proportion of births to women 35 years and older can account for a halving of the estimated percentage of DS births to this age group and a drop in the estimated crude incidence of DS from 1.33/1,000 births in 1960 to 0.99/1,000 births in 1978. Epidemiologic studies suggest that among women 35 years and older, the risk of having a child with DS has not changed. With the present distribution of maternal ages, prenatal diagnosis among women 35 years and older can result in no more than a 20% decrease in the crude incidence of DS. With continued use of prenatal diagnosis among older gravidas, upward of 80% of DS births will occur to younger mothers.

(JAMA 1981;246:758-760)