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Chorionic Villus Sampling

What is Chorionic Villus Sampling (CVS)?

CVS is the withdrawal of a small amount of chorionic villi (placental tissue) through the woman’s cervix or her abdomen. The chorionic villi are cells within the placenta and have the same genetic information as the fetus (unborn baby). CVS detects over 98% of chromosome abnormalities. Typically, the CVS procedure is performed between 10 and 14 weeks gestation (counting from the first day of the last menstrual period). Results of the CVS are available in 10 to 14 days. A preliminary result may be available within 1-2 days.

Before the CVS procedure, an ultrasound exam is done to look at the fetus, uterus and placenta. The procedure consists of placing a very thin needle or catheter into the placenta while watching with ultrasound. A small amount of chorionic villi are removed. Most women describe some cramping with the CVS procedure.

What tests can be done on chorionic villi?

Different tests can be done on chorionic villi depending on the woman’s family and medical history. It is important to realize that CVS does not test for all genetic conditions. CVS does not test for birth defects.

  • Testing for chromosome abnormalities
     

    • The chorionic villi are cells within the placenta and have the same genetic information as the fetus (unborn baby). Test results are usually available within two weeks and detect over 98% of all chromosome abnormalities.

    Click here for more information about chromosomes and chromosome abnormalities.

  • Testing for inherited genetic conditions
     

    • You may know that you are at higher risk of carrying a fetus with a certain inherited genetic condition. This risk may be known because you have a family member that has been diagnosed with a genetic condition or you and your partner have had carrier testing. Depending on your family and medical history, testing for a specific genetic condition may be available. It is important to realize that not all genetic conditions can be tested for by CVS and CVS does not test for all genetic conditions

What are the limitations of the CVS results?

A normal result is great news and reassuring. Unfortunately a normal result does not rule out most birth defects, genetic conditions, mental retardation, or autism.

What are the risks of CVS?

The risk of miscarriage following a CVS is estimated to be less than 1 in 300. Some women will have uterine cramping, leakage of fluid or bleeding from the vagina following a CVS. Most of them do well and do not have a miscarriage.

Infection is very rare following a CVS.

What are my options?

Your options will depend on how far along you are in your pregnancy. If you are in the first trimester (less than 12 weeks gestation) you may choose to have first trimester screening, chorionic villus sampling, expanded AFP screening, or amniocentesis. If you are over 13 weeks gestation your options are expanded AFP screening or amniocentesis. You can decide to decline all genetic screening and testing. Only you can make the best choice for you and your family.

Click here for more information on prenatal testing options.

Who should have CVS?

Women with an increased risk of having a fetus with a chromosome abnormality or inherited genetic condition may wish to consider having a CVS. One of the advantages of CVS over amniocentesis is that test results are available much earlier in the pregnancy.

Some of the more common reasons a woman considers a CVS are:

  • Advanced maternal age
  • Family history of inherited genetic condition
  • First Trimester screening indicates an increased risk of chromosomal abnormality
  • Abnormality noted on ultrasound exam

Click here for more information.