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Am Fam Physician. 2000;62(4):837-838

See related article on Down syndrome.

What is Down syndrome?

Down syndrome is one of the most common genetic disorders. It's caused by the presence of an extra copy of chromosome number 21. This condition is called trisomy 21.

What problems do babies with Down syndrome have?

Down syndrome usually causes mild to moderate mental retardation, or slow mental growth. Almost half of babies with Down syndrome are born with heart problems. Some of these problems can only be fixed with surgery. Some babies with Down syndrome have intestinal problems, vision trouble or hearing loss. Many of these problems can be treated.

Are some people more likely than others to have a baby with Down syndrome?

If you have already had a baby with Down syndrome, you are more likely to have another one. If you have been diagnosed with a chromosome abnormality, you have an increased risk of having a baby with Down syndrome.

The risk of Down syndrome increases with the age of the mother, as shown in this table:

Mother's ageChance of having a baby with Down syndrome
20 years1 in 1,600
25 years1 in 1,300
30 years1 in 1,000
35 years1 in 365
40 years1 in 90
45 years1 in 30

Can Down syndrome be diagnosed during my pregnancy?

Amniocentesis and chorionic villus sampling are two tests that can be used to look for Down syndrome during the first half of your pregnancy. However, these tests can sometimes cause a miscarriage. Therefore, these tests are used only when there is a high chance of a genetic problem in the baby.

Is there another way to tell if my baby might have Down syndrome?

A blood test called the “triple screen” can be done between the 15th and the 18th weeks of pregnancy. The triple screen cannot tell for sure if your baby has Down syndrome, but it can tell if the risk is higher. If the test is positive, it means your risk of having a baby with Down syndrome is higher. But remember that most women with a positive triple screen have babies without Down syndrome.

A negative triple screen means that the chance of Down syndrome is low. However, it doesn't guarantee a baby without Down syndrome.

Sources for Information About Down Syndrome

You can call or write to the following organizations for more information:

  • March of Dimes Birth Defects Foundation

  • 1275 Mamaroneck Ave.

  • White Plains, NY 10605

  • 1-888-MODIMES (663-4637)

  • Web address: http://www.modimes.org

  • National Institute of Child Health and Human Development

  • NICHD Clearinghouse

  • PO Box 3006 Rockville, MD 20847

  • 1-800-370-2943

  • Web address: http://www.nichd.nih.gov

  • Ask for the brochure, “Facts about Down Syndrome” (available in English and Spanish).

  • National Down Syndrome Society

  • 666 Broadway St.

  • New York, NY 10012

  • 1-800-221-4602; 212-460-9330

  • Web address: http://www.ndss.org

  • National Down Syndrome Congress

  • 7000 Peachtree-Dunwoody Rd. NE, Bldg. 5, Suite 100

  • Atlanta, GA 30328-1662

  • 1-800-232-6372; 770-604-9500

  • Web address: http://www.ndsccenter.org

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