What Is Chorionic Villus Sampling (CVS)?

A chorionic villus sampling prenatal test checks cells from the placenta (which are identical to cells from the fetus) to see if they have a chromosomal abnormality (such as Down syndrome).

A CVS can be done from weeks 10 to 13 in a woman's pregnancy. It's a diagnostic test rather than a screening test. That means that it can tell for sure whether a baby will be born with a specific chromosomal disorder.

Why Is Chorionic Villus Sampling Done?

This test is offered to all pregnant women, but in particular those whose babies are at higher risk for a chromosomal abnormality. These include pregnant women who are older, already have a baby with a chromosomal disorder, or have had an abnormal screening test.

The CVS is considered an alternative to an amniocentesis because it can be done earlier in pregnancy, giving expectant parents more time to receive counseling and make decisions. Unlike amniocentesis, CVS does not provide information on neural tube defects like spina bifida. The risks of CVS are higher than with amniocentesis, so the risks and benefits of the test must be weighed.

Should I Have a CVS?

Most pregnant women who are not high risk will not need this test. But your health care provider may recommend this test if you:

  • are older than age 35
  • have a family history of genetic disorders (or a partner who does)
  • have a previous child with a genetic disorder or had a previous pregnancy with a chromosomal abnormality
  • have had an earlier screening test that indicates that there may be a concern

What Happens During CVS?

Chorionic villi are tiny finger-like units in the placenta (which provides nutrients from the mother to the fetus through the umbilical cord). They have the same chromosomes and genetic makeup as the fetus.

During a CVS, some cells from the chorionic villi are removed and tested for chromosomal abnormalities such as Down syndrome, Tay-Sachs disease, and fragile X syndrome.

This test can be done two ways:

  • Transcervical: Using ultrasound as a guide, a thin tube is passed from the vagina into the cervix. Gentle suction removes a sample of tissue from the chorionic villi.
  • Transabdominal: A needle is inserted through the abdominal wall with ultrasound guidance and a sample of the chorionic villi is removed.

Some women find that CVS is painless. Others feel cramping, similar to period cramps, while the sample is taken. After the sample is taken, the doctor may check the fetus' heart rate. You should rest for several hours after the test.

Possible risks of this test include:

  • about a 1% risk of miscarriage (the risk is higher with the transcervical method than with the transabdominal method)
  • infection
  • spotting or bleeding (this is more common with the transcervical method)
  • birth defects when the test is done too early in pregnancy

When Is CVS Done?

Chorionic villus sampling testing is done at 10 to 13 weeks.

When Are the Results Available?

Results are usually available within a few hours to a couple of days, depending on what the test is being used to look for.

Back to Articles

Related Articles

Prenatal Genetic Counseling

Genetic counselors work with people who are either planning to have a baby or are pregnant to determine whether they carry the genes for certain inherited disorders. Find out more.

Read More

Prenatal Test: First Trimester Screening

The first trimester screening (or first trimester screen) includes a blood test and an ultrasound exam. It's done to see if a fetus is at risk for a chromosomal abnormality or birth defect.

Read More

Prenatal Test: Ultrasound

A prenatal ultrasound is a safe and painless test that shows a baby's shape and position. It can be done in the first, second, or third trimester of pregnancy.

Read More

Prenatal Tests: FAQs

Every parent-to-be hopes for a healthy baby, but it can be hard not to worry. Find out what tests can keep you informed of your health — and your baby's — throughout pregnancy.

Read More

Prenatal Tests: First Trimester

Find out what tests may be offered to you during the first trimester of pregnancy.

Read More

Prenatal Tests: Second Trimester

Find out what tests may be offered to you during weeks 13 through 26 of pregnancy.

Read More

Prenatal Tests: Third Trimester

Find out what tests may be offered to you during weeks 27 through 40 of pregnancy.

Read More

Birth Defects

Some birth defects are minor and cause no problems; others cause major disabilities. Learn about the different types of birth defects, and how to help prevent them.

Read More

Medical Care During Pregnancy

The sooner in pregnancy good care begins, the better for the health of both moms and their babies. Here's what to expect.

Read More

Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.