Did you know? One in every 691 babies in the United States is born with Down syndrome, making Down syndrome the most common chromosomal condition. 21 March 2014 will mark the 9th anniversary of World Down Syndrome Day. Each year the voice of people with Down syndrome, and those who live and work with them, grows louder. But there is still so much more to do. To learn more, visit the World Down Syndrome Day website.