Chorionic villus sampling (CVS) is a prenatal diagnostic test that can diagnose or rule out chromosome abnormalities such as Down syndrome and certain genetic disorders such as cystic fibrosis in the baby. CVS is usually done between 10 to12 weeks of pregnancy.
To conduct this test, a small amount of tissue from the developing placenta called chorionic villi is obtained. The cells from this tissue are analyzed by a specialized genetics laboratory. The results are sent to your doctor and are usually available in 10 to 14 days.
The sample of chorionic villi tissue can be obtained by inserting a needle through mother’s abdomen into the placenta or by inserting a thin, hollow tube, called a catheter, through mother’s cervix into the placenta. In both methods, an ultrasound is used during the procedure. A specially trained doctor and other highly trained professionals perform your sampling procedure. With chorionic villi sampling, there is a small risk of miscarriage, about 1 in 100 (1%). The genetic counselor and your doctor can talk with you about the risk and benefits of the test.
The advantage of chorionic villi sampling is that diagnosis can be made during the first trimester of pregnancy. Information about neural tube defects cannot be obtained at the time of chorionic villus sampling. To learn about the risk of neural tube defects, further testing will be necessary in your second trimester such as maternal serum alpha-fetoprotein (AFP) test.
