What is Chorionic Villus Sampling?

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  • Written By: Mary McMahon
  • Edited By: Bronwyn Harris
  • Last Modified Date: 17 January 2019
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Chorionic Villus Sampling (CVS) is a prenatal diagnostic test which can be used to identify abnormalities in a fetus. The test is used to look for chromosomal abnormalities which may result in birth defects, and it can test for several other conditions as well. CVS does carry some risk of miscarriage or complications; a doctor who offers Chorionic Villus Sampling should also discuss risks and benefits of the procedure with the patient.

The procedure involves taking a small sample of the chorionic villus, part of the tissue which makes up the placenta. Since this tissue is fetal in origin, it can be analyzed for defects and abnormalities, such as trisomy, an abnormal number of chromosomes. Because the procedure is invasive, it can lead to infection, breakthrough breaking, and leaking of amniotic fluids. In around one of 200 cases, Chorionic Villus Sampling may lead to miscarriage.

Usually, Chorionic Villus Sampling is performed as an outpatient procedure, with the assistance of ultrasound to visualize the abdomen. Ultrasound ensures that the baby is healthy throughout the procedure, and that the right tissue is sampled. In some cases, the sample is taken with a catheter which is threaded through the uterus, and in other cases a sample is taken with a needle which is inserted through the abdomen. In all instances, the patient should take it easy for several days after the procedure.


The primary advantage of Chorionic Villus Sampling is that it can be carried out earlier than some other diagnostic tests, like amniocentesis. A CVS procedure can be undertaken at around 10 weeks, so women who are at increased risk can address their fears early on in the pregnancy. Prenatal testing is strongly recommended for women over 35, since their infants are at greater risk of birth defects, and for women with a family or personal history of genetic disorders.

In many cases, prospective parents must attend a genetic counseling session before Chorionic Villus Sampling, to make sure that both parents understand the potential ramifications of the procedure. After the results are returned, in one to seven days, the parents meet with the doctor to discuss them. Negative results suggest that the fetus is healthy and viable, while positive results may require further action from the parents. It is important to remember that both false negatives and positives do happen with prenatal testing, so parents should not be afraid to seek out a second opinion or request further testing.



Discuss this Article

Post 3

@anamur-- You are right. They are similar procedures and I believe the risks are the same with both of them. The only difference is that with amniocentesis, they take a sample from the amniotic fluid, not from the placenta as they do with CVS. My daughter has had amniocentesis done and my niece had CVS done. Both had the same risks of infection, bleeding, cramps and so forth. I don't think one is safer or better than the other one.

Post 2

My sister had an amniocentesis when she was 15 weeks pregnant. This was also done to check for genetic defects. The procedure the article describes about chorionic villus sampling and the risks sound real similar to amniocentesis. Is it the same thing? Why is the name different?

Post 1

Did you guys know that down syndrome is not genetically inherited? I just read about this and that's why I think that pregnant woman should get a CVS done when it's safe to do so. All babies are at risk for some genetic defects whether it's in the family or not. This test can prevent a lot of future problems for both the child and parent.

Of course there are some people who oppose CVS testing on moral and religious grounds. That is of course a different argument and I cannot say anything for people deciding not to do it for those reasons. I also understand that it may be scary for women who have had miscarriages before, since the risks are there. But aside from these circumstances, I think that CVS should be considered by all expecting couples.

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