Download PDF

What Is Down Syndrome?

Down syndrome is a common birth defect that includes mental retardation and often heart problems. Children with Down syndrome have round faces and almond-shaped eyes that slant upward. They look more like each other than like their family members. Although the leaming ability of people with Down syndrome varies, all have some degree of mental retardation.

What Causes Down Syndrome?

The egg from the mother and the sperm from the father both carry chromosomes. Chromosomes are bits of genetic material. Having too few or too many chromosomes can cause birth defects. Down syndrome happens when the egg and sperm join together, and the baby that is formed gets an extra chromosome.

What Are the Chances of Having a Baby With Down Syndrome?

The chance of having a baby with Down syndrome gets higher as women get older. If you are less than 30 years old when you have your baby, your chance is less than 1 in 1000. If you are 35 years old, your chance is a bit higher than 1 in 400.

How Can Down Syndrome Be Detected During Pregnancy?

There are two types of tests for Down syndrome. Screening tests are blood tests and/or sonograms. These tests tell you what the chance is that your baby has Down syndrome. The other type of test is a diagnostic test. This test will tell you for sure if your baby has Down syndrome.

What Do Screening Tests for Down Syndrome Tell Me?

The screening test result is a number. The number tells you the chance your baby will have Down syndrome. If the result says I in 400, this means 399 women with this result will not have a baby with Down syndrome, and I person will have a baby with Down syndrome. There are several different screening tests available, and each gives you slightly different information. The back side of this handout tells you about the screening tests for Down syndrome that are available.

What Diagnostic Tests Can Tell Me For Sure if my Baby Has Down Syndrome?

The 2 tests that can tell you for sure are CVS and amniocentesis. Both of these tests look at the chromosomes in a few of the baby’s cells. The cells are taken with a very thin needle from your bag of water or your placenta. The needle goes through your abdomen or vagina. A small number of women (about I in 100 women who have a CVS test and about I in 200 women who have an amniocentesis) who have one of these tests will have a miscarriage.

Should I Have a Screening Test or a Diagnostic Test for Down Syndrome?

There is not a single best answer for all pregnant women. Talk with your family, friends, and health care provider to make a decision that is right for you. When considering these tests for Down syndrome, it is important to remember that they do not find all the birth defects that can occur.


For More Information

The March of Dimes Web site has infonnation on Down syndrome. genetic testing. and other birth defects. National Institute of Child Health and Human Development

Facts About Down Syndrome htm

This page may be reproduced for noncommercial use by health care professionals to share with clients. Any other reproduction is subject to JMWH/ approval. The information and recommendation” appearing on this page are appropriate in most instances, but they are not a substitute for medical diagnosis. For specific information concerning your personal medical condition, JMWH suggests that you consult your health care provider.