CVS Prenatal Test - Chorionic Villus Sampling

This Fetal Genetic Test Carries a Small Risk of Miscarriage

Ultrasound Biometry Of The Fetus
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Chorionic villus sampling (CVS) is a prenatal test that checks for serious chromosome disorders in the developing baby. The test involves taking a sample from the chorionic villi, a part of the placenta, and analyzing the genetic makeup of the tissue. Current research shows that CVS does not carry a higher risk of miscarriage than amniocentesis. 

CVS vs Amniocentesis

Older statistics showed that the CVS test carried a higher risk of miscarriage than amniocentesis, but research now shows that the risk is about the same (roughly 1 in 400).

The main benefit of CVS: It can be performed earlier in pregnancy, at around 10 to 12 weeks. 

The main downside of CVS: It is more likely than amniocentesis to show inconclusive results and, unlike amniocentesis, it cannot offer information on neural tube defects.

Who Should Get the CVS Prenatal Test?

CVS is usually offered to moms-to-be who have a higher than average risk of having a baby affected by a serious genetic disorder.

These women include known carriers for conditions like Tay-Sachs Disease or severe metabolic disorders

The goal is to be able to tell women as early as possible whether or not their babies will inherit the disorder.

Because screening tests such as alphafetoprotein results or the triple/quad screen test are usually done later in pregnancy, most pregnant women who have concerning results on these tests will be offered amniocentesis rather than CVS.

What the Results of Chorionic Villus Sampling Tell You

A CVS prenatal test can detect chromosome disorders and genetic abnormalities in the placental tissue.

CVS is considered about 99 percent accurate for diagnosing genetic disorders.

There are many serious conditions that parents may be concerned about when they consider a CVS. Although the CVS test can detect Down syndrome, it is not exclusively a test for this genetic condition. 

In contrast to an amniocentesis, a CVS cannot provide information neural tube defects.

What to Expect From the Test

You do not need to do anything specific to prepare for the test in most cases. The test can be painful but is usually over in a few minutes. CVS may be performed:

Transabdominally: A long needle is inserted through the abdomen, similar to an amniocentesis.


Transcervically: This is similar to having a pap smear.

If You're Considering a CVS Test

If your doctor has recommended that you have a CVS test, don't be afraid to ask a lot of questions if you have them. A few things to keep in mind: 

  • Newer research suggests that the actual risk of miscarriage after a CVS or an amniocentesis is much lower than the older estimates. Physicians who perform the procedure regularly are likely to have the lowest miscarriage rates.
  • It's normal to be apprehensive about having prenatal tests done that may carry a risk of miscarriage, and it's fine to decline these tests if you're not comfortable with that risk.
  • Many parents are uncomfortable with the risks of a CVS, or may have a stance that they would not terminate a pregnancy regardless of the results. For them, the test is not worth pursuing. These viewpoints are perfectly valid, especially since the CVS merely provides information. Usually there is no prenatal treatment for the disorders diagnosed through CVS. 
  • Some parents prefer to wait a few extra weeks and have an amniocentesis if their triple/quad screen test or ultrasound test seems to indicate problems. They may choose to do this because, unlike CVS, amniocentesis can evaluate for neural tube defects.
  • Parents who should most consider a CVS are those who have a high risk of conceiving a baby with a serious disorder and a desire to confirm or rule out the diagnosis as early as possible.


Chorionic Villus Sampling: CVS. American Pregnancy Association. Accessed: Mar. 12, 2009. 

Chorionic Villus Sampling (CVS). March of Dimes. Quick Reference: Fact Sheets. Accessed: Mar. 12, 2009. 

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