Skip to content
My WebMD Sign In, Sign Up

Children's Health

Select An Article
Font Size

Understanding Down Syndrome -- the Basics

What Is Down Syndrome?

Down syndrome is one of the most common genetic birth defects. Usually, children born with the condition have some degree of mental retardation, as well as characteristic physical features. Many of these children also have other health problems.

Each year in the U.S., approximately one in every 800 to 1,000 newborns has Down syndrome. This results in approximately 5,000 children born with Down syndrome each year. 

Understanding Down Syndrome

Find out more about Down syndrome:

Basics

Symptoms

Diagnosis and Treatment

In the U.S. today, Down syndrome affects approximately 350,000 people. As many as 80% of adults with this condition reach age 55, and many live longer.

The most common form of Down syndrome is often called "trisomy 21," because individuals with this condition have three copies of the 21st chromosome.

What Causes Down Syndrome?

Normally, each cell in the human body contains 23 pairs of chromosomes, which contain the genetic material that determines all our inherited characteristics. We receive half of each chromosome pair from our mother and the other half from our father. Individuals with the most common form of Down syndrome, trisomy 21, have an extra 21st chromosome.

No one knows exactly why this chromosomal error occurs, but it does appear to be related to the age of the mother. At age 25, a woman has a one in 1,250 risk for having a child with Down syndrome. The risk increases to one in 952 at age 30, to one in 378 at age 35, to one in 106 at age 40 and one in 35 at age 45. However, 80% of children born with Down syndrome are born to mothers under the age of 35. This is because most babies, in general, are born to younger women.

Be sure to check with your doctor if you are pregnant or plan to become pregnant if you have a family history of Down syndrome.

WebMD Medical Reference

Reviewed by Patricia Quinn, MD on March 09, 2014
Next Article:

Today on WebMD

child with red rash on cheeks
What’s that rash?
plate of fruit and veggies
How healthy is your child’s diet?
 
smiling baby
Treating diarrhea, fever and more.
Middle school band practice
Understanding your child’s changing body.
 

worried kid
fitArticle
boy on father's shoulder
Article
 
Child with red rash on cheeks
Slideshow
girl thinking
Article
 

babyapp
New
Child with adhd
Slideshow
 
rl with friends
fitSlideshow
Syringes and graph illustration
Tool