Health & Pregnancy

Chorionic villus sampling (CVS) is a test done during early pregnancy that can find certain problems with your baby (fetus). It is generally done when either you or the father has a disease that runs in the family (genetic disorder). It may also be done when you are over age 35-being over 35 increases your chance of having a baby with a chromosome defect.

Chorionic villi are tiny finger-shaped growths found in the placenta. The genetic material in chorionic villus cells is the same as that in the baby's cells. During CVS, a sample of the chorionic villus cells is taken for biopsy. The chorionic villus cells are checked for problems. The procedure is generally done late in the first trimester, most often between the 10th and 12th weeks.

The chorionic villus sample can be collected by putting a thin flexible tube (catheter) through the vagina and cervix into the placenta. The sample can also be collected through a long, thin needle put through the belly into the placenta. Ultrasound is used to guide the catheter or needle into the correct spot for collecting the sample.

If you have a family history of certain diseases, CVS can be used to find genetic disorders, such as Tay-Sachs disease or hemophilia. It can also find chromosomal birth defects, such as Down syndrome. CVS cannot find neural tube defects and it cannot be used to see if the baby's lungs are mature.

Chorionic villus sampling can be done earlier in pregnancy (at 10 to 12 weeks) than amniocentesis (usually done at 15 to 20 weeks). This allows you to know the health of your baby and make an earlier decision whether to continue or end the pregnancy. Results of CVS can be available sooner than amniocentesis results.

Pregnancy: Should I Have Chorionic Villus Sampling?

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Why It Is Done

Chorionic villus sampling may be done during your first trimester of pregnancy to find certain birth defects.

You may choose to have this test because:

• Of your age. As you get older, you have a greater chance of having a baby with a birth defect. Many doctors use 35 and older as the age for higher risk.
• You want to know for sure if your baby has a certain health problem. This may help you decide early whether you want to continue your pregnancy or make plans to care for a sick child.
• You or the baby's father carries an abnormal gene that is known to cause a disease, such as Tay-Sachs disease, sickle cell anemia, or cystic fibrosis.
• You or the baby's father has a family history of a genetic disorder or birth defect.
• Screening tests suggest that your chance of having a baby with a genetic disorder or birth defect is higher than average.