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Definition of Chorionic Villus Sampling
Chorionic Villi Sampling (CVS) is a diagnostic procedure, also called chorionic villus sampling, in which the obstetrician removes small clusters of cells from the hairlike edges of the placenta, the chorionic villi, during pregnancy.
The cells in this sample provide genetic information about the fetus that can rule out or diagnose genetic disorders such as cystic fibrosis and tay-sachs disease, neural tube defects such as spina bifida, or chromosomal disorders such as down syndrome.
The obstetrician can perform Chorionic Villi Sampling (CVS) in the first trimester, usually around the 11th week, providing information about potential health concerns early in the pregnancy to allow the woman and her partner to consider possible treatment options as well as whether, with severe disorders or deformities, to continue the pregnancy.
To withdraw the sample of cells the obstetrician may insert a needle through the abdominal wall and into the uterus, similar to amniocentesis, or may guide a very small catheter through the vagina and cervix into the uterus. The obstetrician first numbs either the site on the abdomen or the cervix with a local anesthetic, then uses ultrasound to help place the needle or the catheter.
After the procedure the woman may feel mild cramping or experience slight bleeding, which are the main risks associated with Chorionic Villi Sampling (CVS). Rarely CVS can cause spontaneous abortion (loss of the pregnancy), though the risk with CVS less than the risk with amniocentesis, another prenatal diagnostic procedure, because CVS does not require penetration of the amniotic sac.
The findings available through Chorionic Villi Sampling (CVS) are not always as definitive as the results of amniocentesis. The advantages of CVS over amniocentesis, however, are twofold. First, the obstetrician can conduct CVS in the first trimester though cannot perform amniocentesis until well into the second trimester.
Second, the risk for complications, including injury to the fetus and spontaneous abortion, is lower with Chorionic Villi Sampling (CVS). It is important to discuss and thoroughly understand the reasons for either procedure.
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