Chorionic Villus Sampling (CVS)

CVS (Chorionic Villus Sampling)

What To Think About

• Normal results from chorionic villus sampling (CVS) do not guarantee that your baby will be healthy. CVS cannot find neural tube defects.
• Amniocentesis (which is usually done later in the pregnancy than CVS) can also be used to find diseases of the fetus, such as neural tube defects. If CVS does not show clear results, amniocentesis may need to be done.
• In one study of highly trained providers, both CVS and amniocentesis had about a 1 in 400 chance of miscarriage.¹ Some studies have shown a slightly higher risk, from 2 to 4 in 400.² This greater risk may be more likely in medical centres with less experienced providers, especially for CVS. For more information, see the medical test Amniocentesis.
• CVS is done if you are at high risk for having a baby with a chromosomal birth defect (such as Down syndrome) or a family genetic disease (such as Tay-Sachs disease or hemophilia). The benefits of this test often outweigh the risks. Genetic diseases and birth defects can be found earlier in pregnancy by CVS than by amniocentesis. This allows you to make an earlier decision whether to continue or end the pregnancy.
• The results of CVS may vary depending on how the sample was taken.
• If you have a vaginal infection (such as a vaginal yeast infection or genital herpes), a belly procedure will be used instead of a vaginal procedure.
• CVS causes bleeding that could lead to mixing of your blood and your baby's about half of the time. If you have Rh-negative blood, you will be given the Rh immune globulin vaccine (such as RhoGAM) to prevent Rh sensitization which could harm your baby if he or she has Rh-positive blood.

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Author:	Jan Nissl, RN, BS Sydney Youngerman-Cole, RN, BSN, RNC	Last Updated: October 12, 2006
Medical Review:	Renée M. Crichlow, MD - Family Medicine Siobhan M. Dolan, MD, MPH - Reproductive Genetics Liisa Honey, MD, FRCSC - Obstetrics and Gynecology
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