Chorionic villus sampling (CVS) is a test that detects genetic abnormalities. Sampling is done early in pregnancy, usually between the 9th and 11th weeks.
Ultrasound is used to locate the fetus and the placenta. A small piece of tissue is removed from the placental area with an instrument placed through the cervix or with a needle inserted through the abdomen.
The advantage of CVS is an earlier diagnosis than amniocentesis of a problem, if one exists. The test can determine various fetal problems, such as Down syndrome, Tay-Sachs disease and cystic fibrosis. Some women choose to have this test because they want results earlier so they can make decisions about the pregnancy.
There is a small risk of miscarriage with this procedure. The test should be performed only by someone who has experience doing it.
CVS or Amniocentesis?
CVS can be done much earlier in pregnancy than amniocentesis, and results are available in about a week. If the woman decides to terminate the pregnancy after learning results of the test, the procedure can be performed earlier in pregnancy and may carry fewer risks. On the other hand, the risk of disturbing a normal pregnancy is slightly higher with CVS than with amniocentesis.
Each woman's pregnancy is different. Discuss CVS with your doctor. He or she will be able to help you determine if your particular case requires it.