Chorionic villus sampling (CVS) is a prenatal test in which a sample of chorionic villi is removed from the placenta for testing. The sample can be taken through the cervix (transcervical) or the abdominal wall (transabdominal).

During pregnancy, the placenta provides oxygen and nutrients to the growing baby and removes waste products from the baby's blood. The chorionic villi are wispy projections of placental tissue that share the baby's genetic makeup.

Chorionic villus sampling is usually done between weeks 10 and 13 of pregnancy — earlier than other prenatal diagnostic tests, such as amniocentesis. Chorionic villus sampling can reveal whether a baby has a chromosomal condition, such as Down syndrome. Chorionic villus sampling can also be used to test for other genetic conditions, such as cystic fibrosis.

Although chorionic villus sampling can provide valuable information about your baby's health, it's important to understand the risks — and be prepared for the results.

Oct. 17, 2015