What is Down syndrome?
Down syndrome is a chromosomal condition caused by extra genetic material. Typically, our cells contain 23 pairs of chromosomes. In the case of Down syndrome, a person has an extra full or partial copy of chromosome 21. This extra genetic material changes how the body and brain develop. People with Down syndrome have a few common physical traits, but each individual is unique and can lead a healthy active life.
Down syndrome is the most common chromosomal condition in the United States, but we don’t know for sure why Down syndrome happens. Although it’s a genetic condition, it’s not something that is passed on from the parents or family to the baby (inherited). In fact, most cases happen because in the early stages of the baby’s development, there is a problem when the cells are dividing. However, there are some factors that may increase the risk of having a baby with Down syndrome. These include:
- Mother’s age. Even though about 80 percent of babies with Down syndrome are born to women aged 35 or less, the risk of Down syndrome actually increases as you get older.
- Having had a baby with Down syndrome. If you’ve had a baby with Down syndrome, talk to a genetic counselor to better understand how likely you are to have another baby affected by this condition.
- Being a carrier of a genetic translocation. Both men and women can pass a genetic translocation to their baby. However, it’s important to know these cases are rare.
During pregnancy your health care provider will offer screening tests to see if your baby is more likely to have Down syndrome. These tests are offered to all pregnant women as part of regular prenatal care. However, a screening test won’t tell you for sure if your baby has Down syndrome. It only tells you if there is a higher risk. To know for sure you will need a diagnostic test.
How do you know if your baby has Down syndrome?
Your provider will recommend a diagnostic test based on the results of your screening test. A diagnostic test will confirm if a baby has Down syndrome. There are few diagnostic tests:
- Amniocentesis (also called amnio). This test checks the amniotic fluid surrounding your baby in the uterus to check for Down syndrome. You can get an amnio at 15 to 20 weeks of pregnancy.
- Chorionic villus sampling (also called CVS). This test checks the tissue from the placenta to see if a baby has Down syndrome. You can get a CVS at 10 to 13 weeks of pregnancy.
- Cordocentesis (also called percutaneous umbilical cord sampling or PUBS). You can get this test between 18 and 22 weeks of pregnancy. There’s a much greater risk of miscarriage with cordocentesis than with an amnio or a CVS. If other tests are unclear and your provider can’t confirm if your baby has Down syndrome any other way, a cordocentesis may be recommended.
To learn more visit:
National Down Syndrome Society
Centers for Disease Control and Prevention (National Center of Birth Defects and Developmental Disabilities)