Down syndrome is the most common chromosomal abnormality. Each year approximately 3,000 to 5,000 children are born with this chromosome disorder and it is believed there are about 250,000 families in the United States of America who are affected by Down syndrome. Birth rates are highest among mothers of advanced maternal age however 80% of all children with Down syndrome are born to mothers younger than 35 years. Down syndrome occurs in people of all races and economic levels.
Down syndrome epidemiology and demographics
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