Down syndrome prevalence at birth--United States, 1983-1990.

Down syndrome* (DS) (trisomy 21) is one of the most serious and frequently reported birth defects among live-born infants and an important cause of mental retardation. The prevalence of DS at birth increases with increasing maternal age. Because national population-based estimates of DS have been limited, CDC analyzed data from 17 states with population-based birth defects surveillance programs to determine the birth prevalence of DS and describe trends in DS in the United States during 1983-1990. This report summarizes the findings of the analysis.