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What is chorionic villus sampling?

If you wish to find out detailed genetic information pertaining to your baby’s health, CVS can provide information about chromosomal abnormalities, such as Down syndrome and other genetic conditions such as cystic fibrosis. CVS is a prenatal test that involves taking a sample of placental tissue using a thin needle through your abdomen or a catheter through your cervix. Testing is available for a wide array of genetic disorders depending on your family history and availability of laboratory testing at the time of the procedure.

CVS is an alternative to amniocentesis, but the benefit of CVS is that it can be done sooner in your pregnancy, roughly between 11 and 13 weeks. If you have a CVS, it will not provide information on spina bifida or any other birth defects. Therefore, you will need to have an alpha feto protein blood test at 16-18 weeks to test for these defects as well as an ultrasound to assess fetal anatomy.

If you have twins or other multiples, you will usually need sampling from each placenta.

In rare circumstances, you may not be a candidate for CVS or your results from the CVS may not be 100 percent conclusive, which may require an amniocentesis.

Benefits of CVS

As compared with screening tests, CVS is a diagnostic test that provides definitive genetic information about your baby. The main advantage of CVS over amniocentesis is that it is performed at an earlier time during a pregnancy. With CVS, results are generally ready by 14 weeks of pregnancy. If you choose to get a CVS, this will give you early reassurance if the results are normal, or more time to consider your medical options if problems are detected.

Our approach

During your first prenatal visit, our expert Maternal-Fetal Medicine and Genetics specialists will discuss all your options for screening and genetic testing. While the information can sometimes be overwhelming, our team, including genetic counselors will take the time to provide a comprehensive overview of the tests we offer to help you make an informed and personalized decision according to what works best for you and your family. When genetic testing is desired in the first trimester, you will be offered a chorionic villus sampling, or CVS, to test for potential genetic abnormalities.

Why it's done

The following reasons are common for CVS testing:

  • You decide you want to test for chromosomal abnormalities
  • You had a screening test that indicated you’re at increased risk for chromosomal abnormalities
  • You have a family history of genetic disorders
  • An ultrasound finding that showed an abnormality


Miscarriage is the main risk associated with CVS sampling. Because it is done during the first trimester, a time when spontaneous miscarriages occur more frequently, it has a slightly higher risk of miscarriage than amniocentesis. The risk of miscarriage after CVS is estimated to be less than 1 in 500.

Side effects after the procedure may include mild cramping and/or spotting. You should call your doctor if you experience fever, heavy bleeding or persistent pain. You will also be advised not to have intercourse 24 hours after the procedure.

What to expect after treatment

If you experience vaginal bleeding or worsening cramping, please contact your physician immediately.

After you receive the results of the test, you will be offered post-test genetic counseling if there is an abnormality. Sometimes your results will warrant additional testing. Our Maternal-Fetal Medicine and Genetics experts will be there to help you interpret the results and counsel you and your family on your options and recommend next best steps for care.

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