Chorionic villus sampling

Chorionic villus sampling (CVS) is a prenatal test. It’s used to diagnose certain birth defects and genetic abnormalities in your baby. Genetic abnormalities are changes in the genes that are passed down to a baby from mom or dad. These genetic changes can cause health problems for a baby.

During CVS, your health care provider takes a small piece of tissue from the placenta. The sample is used to check your baby’s health.

You can get CVS early in pregnancy, between 10 and 13 weeks. CVS isn’t given to all pregnant women because there’s a small chance of miscarriage after the test.

CVS is different from another prenatal test called amniocentesis (also called amnio). Amnio is performed a little later in pregnancy. Talk to your provider about having CVS, amnio or other prenatal tests.

What are some reasons for having CVS?

Your provider should discuss prenatal testing with you and may offer you CVS. And you can ask to have CVS. You may want to have CVS if you’re at risk for having a baby with a genetic abnormality. These risks include:

  • Being 35 or older: The risk of having a baby with certain birth defects or genetic abnormalities, such as Down syndrome, increases as you get older.
  • Having a previous child or pregnancy with a birth defect: If you had a child or a pregnancy with a birth defect in the past, your provider should offer you testing.
  • Abnormal screening test results: If you had abnormal results from a pregnancy screening test, your provider should discuss CVS with you. CVS can provide specific information to confirm if there is an abnormality in the baby. Most babies with abnormal screening test results don’t have problems and are born healthy.
  • Family history of a genetic health problem: If you or your partner has a certain genetic disease (a health condition that gets passed down to a baby from mom or dad), or a close family member with a disease, such as cystic fibrosis or sickle cell anemia, you may want to have CVS.

How is the test done?

The test usually takes 30 to 45 minutes.

A health care provider with expertise in performing CVS takes a tiny piece of tissue from the placenta, which has cells from your baby, to check for problems. The placenta grows with your baby in your uterus (womb). It gives your baby food and oxygen through the umbilical cord.

There are two kinds of CVS:

  1. Testing through the belly (called transabdominal CVS) — Your provider puts a thin needle through your belly into the womb. She then uses the needle to take a small sample of the placenta tissue.
  2. Testing through the cervix (called transcervical CVS) — Your provider places a thin tube through your vagina and cervix (the opening to the uterus that sits at the top of the vagina). The tube gently sucks in a tiny sample of the placenta tissue.

Your provider sends the tissue sample to a lab where it is examined and tested. Test results are usually ready in about 7 days.

Are there any side effects or risks?

Some women find that CVS is painless. Others feel cramping, similar to period cramps, when the sample is taken. Some women who have testing through the cervix say it feels like having a Pap smear.

After CVS, relax for the rest of the day. You may have spotting or cramping for a few hours after the test. Call your health care provider right away if you have heavy bleeding, fever or contractions.

CVS does involve a small risk of miscarriage. The American College of Obstetricians and Gynecologists (ACOG) reports that 1 in 100 (1 percent) women has a miscarriage following testing.

What happens after the test?

In most cases, CVS test results show that a baby is healthy and without birth defects. If the test shows that your baby does have a birth defect, talk to your provider about all of your options. Your baby may be able to be treated with medicines or even surgery before birth. Or there may be treatments or surgery he can have after birth.

Knowing about a birth defect before birth may help you get ready emotionally to care for your baby. You also can plan your baby’s birth with your health care provider. This way, your baby can get any special care she needs right after she is born.

What if you’re not sure about having CVS?

Choosing to have CVS is a personal decision. Talking with genetic counselors, your health care provider, and religious and spiritual leaders can help you make decisions about testing for birth defects during pregnancy.

Ask your provider about other prenatal test options and how you can find a doctor who is trained and experienced in offering specific tests. Learn as much as you can about any prenatal tests your provider recommends to make the right decisions for you and your baby.

Last reviewed: June, 2014