CVS (Chorionic Villi Sampling)

CVS is a diagnostic test performed when a problem is suspected and an earlier diagnosis than that provided by amnio is desired.

Chorionic Villus Sampling (CVS), like amniocentesis, is a test that is capable of diagnosing chromosomal problems such as Trisomy 18. (See How Trisomy 18 is diagnosed for an explanation of the difference between screening and diagnostic tests.) CVS involves taking a small piece of chorionic villi (wisps of tissue that attach the pregnancy sac to the wall of the uterus) and analyzing the cells. These cells normally have the same genetic and biochemical makeup as the fetus, so any chromosomal problems can be diagnosed this way.

This test is usually performed between 10 and 12 weeks after the mother’s last menstrual period. This gives CVS the advantage of providing an earlier diagnosis, since this is several weeks earlier than amniocentesis is performed. CVS is not typically offered to all pregnant women because there is a small risk of miscarriage. Some studies suggest that the risk is slightly higher than that of amniocentesis, but also indicate that using physicians who are experienced in this procedure seems to reduce the risk to that of amniocentesis.

For more information about CVS, see Chorionic Villus Sampling from the March of Dimes.

What if my CVS test shows that my child has Trisomy 18?

If you have a positive diagnosis of Trisomy 18, you will be faced with many decisions. We have created a section to help you face those decisions. See Making Decisions after a Prenatal Diagnosis for more help.