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    Genetic Screening Tests for Women 35 or Older

    Chorionic Villus Sampling (CVS) continued...

    During this test, a small sample of cells, called chorionic villi, is taken from the placenta. Chorionic villi are tiny parts of the placenta that are formed from the fertilized egg, so they have the same genes as your baby. To get the cells, a doctor passes a needle through the vagina or the abdomen, depending on the location of the placenta. The cells are used to check your baby's chromosomes, just like amniocentesis.

    CVS and amniocentesis usually involve genetic counseling, where you speak with a counselor about your risk for genetic disorders. You will also learn about the risks and benefits of the procedures.

    Noninvasive Prenatal Diagnosis

    This new blood test, also called cell-free DNA testing, is used to show whether you are at risk for having a baby with chromosome problems. Because it's done by using a sample of your blood, it's less invasive than amniocentesis or CVS.

    The test is done between 10 and 22 weeks of pregnancy. It finds DNA from your baby floating around in your blood. The result determines the chance that your baby could be born with Down syndrome, trisomy 18, or trisomy 13.

    Noninvasive prenatal diagnosis can detect about 99% of Down syndrome and trisomy 18 cases, which is much better than other blood tests. The majority of trisomy 13 cases can also be detected with this test.

    If the test shows an increased risk for chromosome problems, your doctor may recommend CVS or amniocentesis to confirm the diagnosis.

    Because this is a new test, not all insurers cover it. Check with your insurance company to see whether the cost of the test will be covered.

    WebMD Medical Reference

    Reviewed by Traci C. Johnson, MD, FACOG on August 22, 2014
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