CVS (Chorionic Villus Sampling)

Who Gets the Test?

Your doctor may suggest CVS if your baby has a higher risk of some birth defects. That could be because you are over 35, have a family history of problems, or had unusual results after your first-trimester screening.

What the Test Does

CVS is an alternative to amniocentesis. Like amniocentesis, CVS can diagnose some disorders. It checks your baby's chromosomes for birth defects or genetic disorders. Your doctor takes a sample of cells from the placenta. Then a lab tests the cells to analyze your baby's chromosomes. The lab tests can include the karyotype test, the FISH test, and microarray analysis.

CVS helps rule out some birth defects, such as Down syndrome, Tay-Sachs disease, cystic fibrosis, sickle cell anemia, and others.

The advantage of CVS is that you can get this test five to 10 weeks earlier than amniocentesis. The disadvantage is that it can't detect neural tube defects, such as spina bifida.

CVS is relatively safe. But it is an invasive procedure, and it poses a risk of miscarriage slightly higher than amniocentesis. It also poses a small risk of complications in your baby, such as loss of limbs. Talk to your doctor about the risks. Make sure the test is done by doctor who has a lot of experience doing CVS.

How the Test Is Done

Doctors do the CVS test two different ways. Using ultrasound to guide the way, your doctor may insert a small needle into your belly to take a sample of cells from the placenta. Or, your doctor may insert a thin plastic tube through your vagina to get a sample from the placenta. The test can be uncomfortable, but only lasts about 10 minutes.

What to Know About Test Results

You should get test results in about one week. CVS is very accurate. If your baby does have a problem, you can meet with a genetic counselor and talk about your options.

How Often the Test Is Done During Pregnancy

Probably just once, if at all. If you need it, your doctor will suggest it when you are 10 to 13 weeks pregnant.

Tests Similar to This One

Amniocentesis, karyotype test, FISH test, microarray analysis

WebMD Medical Reference Reviewed by Nivin Todd, MD on May 11, 2016

Sources

SOURCES:

American Academy of Pediatrics healthychildren.org: "Detecting Genetic Abnormalities."

UCSF Medical Center: FAQ: "Chorionic Villus Sampling (CVS)."

Pagana, K.D. Mosby’s Diagnostic and Laboratory Test Reference, 10th ed. Mosby: 2010.

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