Obstetrics - OB Tests and Procedures - Chorionic Villus Sampling

Chorionic Villus Sampling (CVS)

Chorionic villus sampling (CVS) is a test that may be done early in pregnancy. A small sample of tissue is removed from the placenta. The genetic information (chromosomes) in this tissue is the same as the baby's. Genetic specialists analyze the tissue. This test can help you know early in a pregnancy if the baby has a chromosome problem, such as Down syndrome.

CVS is similar to amniocentesis. Amniocentesis is a procedure in which fluid is sampled from the sac surrounding the baby. Amniocentesis is usually done between the 15th and 18th weeks of pregnancy. CVS can be done several weeks earlier than amniocentesis. It is used to test for many of the same problems that amniocentesis tests for. Unlike amniocentesis, however, CVS cannot detect neural tube defects, which are birth defects of the baby's brain or spine. A blood test (alpha-fetoprotein/AFP screening) may be done for this purpose later in the pregnancy.


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