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Am Fam Physician. 2009;79(2):124

See related article on fetal chromosomal abnormalities.

What are genetic screening tests?

They are tests to see if your baby is at risk of a genetic disorder, such as Down syndrome. Genetic disorders happen when your baby does not have the normal number of chromosomes, which contain the baby’s genes, or when there are problems with the brain or spine. Not all pregnant women have these tests. Your doctor will help you decide if these tests are right for you.

How does it work?

Some screening tests are done in the first trimester of pregnancy, and some are done in the second trimester. Your doctor may have you tested in both trimesters, depending on your baby’s risk and the testing method you select.

There are several ways to do the screening. One type of screening (no needles) is an ultrasound. This measures the thickness of the liquid under the skin on your baby’s neck. If the thickness is not normal, your baby may not have the normal number of chromosomes. Your doctor may also do a blood test to check your baby’s risk of having a genetic disorder.

There are two tests that can say for sure if your baby has a genetic disorder. They both have a small risk of causing a miscarriage. One test is called amniocentesis (AM-nee-oh-sen-TEE-sis). This is when the doctor uses a needle to take a small sample of fluid from the bag of water around the baby. The other test is called chorionic villus (core-ee-AH-nick VIL-us) sampling. This is when the doctor uses a needle to take a small sample of tissue from the placenta. This test is done earlier in the pregnancy than amniocentesis.

What should I do after I learn the results?

If the screening shows that your baby has a genetic disorder or is at risk of a genetic disorder, talk to your doctor about your options.

Where can I get more information?

Your doctor

American Academy of Family Physicians

U.S. National Library of Medicine and the National Institutes of Health

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