Dr. MJ Bazos MD, Patient Handout
Down Syndrome: What You Need to Know When You're Pregnant
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:
Risk of Down Syndrome
Mother's age
Chance of having a baby with Down syndrome
20 years
1 in 1,600
25 years
1 in 1,300
30 years
1 in 1,000
35 years
1 in 365
40 years
1 in 90
45 years
1 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 that a baby doesn't have Down syndrome.
Should I be tested?
This decision is up to you. Talk with your doctor about your risk of having a baby with Down syndrome. Think about whether you really want to know if your baby has Down syndrome. The box below lists groups that can give you more information on Down syndrome.
March of Dimes Birth Defects Foundation: www.modimes.org
National Institute of Child Health and Human Development: www.nichd.nih.gov
National Down Syndrome Society: www.ndss.org
National Down Syndrome Congress: www.ndsccenter.org