What to Know About Amniocentesis and Chorionic Villus Sampling

Would you like to know if the baby in your uterus is healthy? If you are like most women, your answer will be "yes." As you may already know, there are numerous tests that can be done during pregnancy to check for abnormalities. Amniocentesis and Chorionic Villus Sampling are two of these tests, whose main purpose is to diagnose genetic or chromosomal defects, but can also provide other valuable information, such as paternity results. These two tests are used for mothers who are at risk for carrying a fetus with a congenital birth defect. This includes women over 35, women with a history of miscarriages or birth defects, and women with a family history of genetic disease. You may have never heard of amniocentesis or chorionich villus sampling, or you may only have a general idea of what's involved. Hopefully this information can help you to be prepared and comfortable if the need should arise for you to have either of these tests done. Amniocentesis Amniocentesis is normally performed in the second trimester, between the 15th and the 18th week of pregnancy. Using an ultrasound as a guide, the health care provider inserts a long needle into the abdomen of the mother and draws out a small amount of amniotic fluid. This test is more than 99% accurate in diagnosing chromosomal disorders like Down syndrome and Edward's syndrome. Unfortunately, there is a small risk of miscarriage of about 0.5%-1% (1 or 2 cases out of 200). Chorionic Villus Sampling (CVS) Chorionic Villus Sampling is normally performed in the first trimester, between the 10th and 12th week of pregnancy. Using an ultrasound as a guide, the health care provider inserts a long, thin tube into the vagina and through the cervix and removes a small amount of chorionic villus from the outside of the sac where the baby develops. Unfortunately, this procedure has a slightly higher risk of miscarriage than amniocentesis of about 1%-3% (1-3 cases out of 100)