Obstetrics and Gynecology

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Chorionic Villus Sampling

What is chorionic villus sampling?  

Chorionic villus sampling (CVS) is a prenatal diagnostic procedure typically performed by a Maternal Fetal Medicine specialist that can be done during the first trimester of pregnancy (typically between 11 and 14 weeks) to test your baby for chromosome and genetic conditions.   

CVS involves getting some of the tissue from the placenta (the chorionic villi) so that the lab can test for chromosome and genetic conditions.  The tissue for testing can be obtained in one of two ways: transcervically, where a catheter can be used to reach the placenta vaginally, or transabdominally, where a small needle can be inserted into the abdomen to reach the placenta. With CVS there is a risk for complications that can lead to a miscarriage.  This risk is significantly less than 1%. 

What does CVS test for?

There are many different types of testing that can be done on CVS samples, including traditional chromosome analysis (karyotype), FISH, chromosomal microarray, and familial mutation testing.  All of this testing is considered to be diagnostic testing for chromosome and genetic conditions, meaning it can typically provide a ‘yes’ or ‘no’ answer, as opposed to screening tests which only tell you the chances or odds. CVS can test for many things, but cannot screen for all medical conditions or birth defects. 

Your physician or genetic counselor can help you understand the available testing options and interpret results.

Who can have a CVS? 

CVS is available to all women who are pregnant and desire to know more information about their baby’s chromosomes.  It is also available to women whose pregnancies are known to be at a higher risk for chromosome and genetic conditions based on screening and ultrasound results or family history.   

It is important to know that prenatal diagnostic tests, like CVS, are always optional. You never have to undergo any if you do not wish to. Anyone who is having prenatal testing should have access to all of the necessary information to make an informed decision about what is right for them and their family.