Down Syndrome

Down syndrome is a genetic condition where people are born with an extra chromosome. Most people have 23 pairs of chromosomes within each cell in their body, for a total of 46. A person diagnosed with Down syndrome has an extra copy of chromosome 21, which means their cells contain 47 total chromosomes instead of 46. This changes the way their brain and body develop.

Who does Down syndrome affect?

Down syndrome can affect anyone. It’s a genetic condition, and it doesn’t happen as a result of something that the parents did before or during pregnancy. The majority of Down syndrome cases happen randomly (sporadically). People don’t usually inherit Down syndrome in an autosomal dominant or recessive pattern during conception when the egg and sperm meet.

What are the risk factors for Down syndrome?

Research is ongoing to learn more about the risk factors of Down syndrome. Studies suggest that the risk of giving birth to a child with Down syndrome increases as the birthing parent ages. Women or people assigned female at birth (AFAB) who are 35 or older are more likely to have a child diagnosed with Down syndrome or another type of genetic condition. Since people AFAB younger than 35 have higher fertility rates, most babies with Down syndrome are born to people under 35.

How common is Down syndrome?

Down syndrome is the most common chromosome-related condition in the United States. An estimated 6,000 babies are born with the condition in the U.S. every year, which equals about 1 in every 700 babies. There are about 200,000 people in the U.S. diagnosed with Down syndrome.