Down syndrome occurs worldwide, and its incidence varies by region and maternal age.
According to the World Health Organization, the estimated incidence of Down syndrome is between 1 in 1,000 to 1 in 1,100 live births worldwide.
However, the incidence is higher among children born to mothers who are 35 years or older. In the United States, about 1 in every 700 babies born has Down syndrome.
Down syndrome is the most common chromosomal disorder, and it affects people of all races and ethnicities. (source: WHO)