A CVS (chorionic villus sampling) is performed to get an early diagnosis of genetic and/or chromosomal abnormalities, such as Down syndrome. It's recommended in cases where there's an increased risk of these defects and expectant parents don't want to wait for an amniocentesis to know for sure (CVS can be done as early as 10 to 12 weeks into pregnancy, while amniocentesis is performed in the second trimester). Having a CVS gives couples time to explore available options should the baby be found to have a problem.
You doctor may recommend CVS if you're over 35, have already had a child with chromosomal or genetic abnormalities, or have a history of such problems in your family. It's important to remember that CVS does have a slight miscarriage risk, but recent research suggests it's not as high as scientists previously thought (about to 1 in 370 procedures, as opposed to the previously cited 1 in 100 stat). CVS cannot test for neural-tube defects like spina bifida.
CVS begins with an ultrasound to confirm your baby's age and to find the placenta. Then, using the ultrasound as a guide, a tiny piece of the chorionic villi (the fingerlike projections of tissue that attach the placenta to the uterus) is removed by inserting a tube through the vagina into your uterus and using gentle suction to collect the tissue, or by inserting a narrow needle through the abdomen and into the uterus to extract it. (The method used depends largely on the position of the placenta.)
The villi sample (which has the same genetic makeup as the baby) is then sent to a lab. The test takes about 30 minutes, after which you should plan to take it easy, since you may have mild cramping and slight spotting. But if you experience any prolonged bleeding or cramping, you should call your doctor right away.
CVS results are more than 99 percent accurate and are usually available within a week or two. If you receive "normal" results, your baby has an excellent chance of being healthy -- but be aware that the test doesn't rule out every possible problem. If your test results indicate an abnormality, you will meet with your doctor and a genetic specialist to discuss your options, which may include further tests.