Down Syndrome and Your Unborn Baby

Down syndrome is a genetic disorder that causes mental retardation and physical defects. It is caused by the presence of an extra copy of chromosome number 21. This condition is called trisomy 21.

Down syndrome usually causes mild to moderate mental retardation, or slow mental growth. Language skills develop slowly in babies who have Down syndrome. About half of babies who have Down syndrome are also born with heart problems, some of which may require surgery. Some babies who have Down syndrome also have intestinal problems, thyroid disease, vision trouble or hearing loss. Many of these problems can be treated with medical attention and educational assistance as the baby gets older.

If you have already had a baby who has Down syndrome, you are more likely to have another one. For every 100 couples who has another baby, 1 will have another who has Down syndrome. If you have been diagnosed with a chromosomal abnormality, you also have an increased risk of having a baby who has Down syndrome.

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

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, there is a slight risk that these tests can cause a miscarriage. Therefore, these tests are used only when there is a high chance of a genetic problem in the baby (such as a mother age 35 or older).

A blood test called the "quad marker screen" can be done between the 15th and the 22nd weeks of pregnancy, but it's more accurate when done between the 16th and 18th weeks. The quad marker screen cannot tell for sure if your baby has Down syndrome or other chromosomal disorders, but it can tell if the risk is higher. If the test is positive, it means your risk of having a baby who has Down syndrome is higher. But remember that many women with a positive quad marker screen have babies that do not have 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.

This decision is up to you. Some women feel better if they know if their baby is at risk so that they can prepare themselves for the possibility of having a baby who has Down syndrome. Your doctor can help you understand your risks and consider the pros and cons of getting tested.