Chorionic villus sampling (CVS) is a test that can detect genetic abnormalities earlier than amniocentesis can. It is usually done between the ninth a eleventh weeks of pregnancy. However, it is not available in all locations.
A chorionic villus is one of the fingerlike projections covering the developing embryo. It contains cells that have the same genetic composition as the embryo. In CVS, a sample of chorionic tissue about the size of a grain of cooked rice is removed. In one method, a suction catheter is inserted into the uterus through the cervix under the visual guidance of ultrasound. In another method, a needle is inserted into the uterus through the abdominal wall. This procedure takes approximately 30 minutes to complete.
The advantages of CVS are that it can be performed early in pregnancy that results can be obtained more quickly than with amniocentesis. Up to 3 or 4 weeks may pass before amniocentesis results are known. The possible risk of CVS include infection, Rh sensitization, bleeding by the woman or baby miscarriage, birth defects, and perforation of the fetal membrane.” In addition studies in England have indicated that fetal limb deformities may result from CVS, especially when it is done early in the pregnancy (before 66 days). Several American studies have failed to confirm this finding, however.