Chorionic villus sampling, or CVS, is a procedure that can be done during the first trimester of pregnancy (usually between 11 and 14 weeks). CVS involves getting some of the tissue from the placenta (the chorionic villi) so that the lab can test for chromosome and genetic conditions.
Because CVS is an invasive procedure, there is a risk of less than 1 in 200 (or 0.5%) for complications that can lead to a miscarriage. That also means that more than 99.5% of women who have a CVS will not have a procedure-related miscarriage. Because of this risk for complications, diagnostic tests like CVS are always optional, and never anything that you would have to do.
There are many different types of testing that can be done on CVS samples, including traditional chromosome analysis (karyotype), FISH, chromosomal microarray, and familial gene 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 screen for many things, but cannot screen for all medical conditions or birth defects, including open neural tube defects.
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