doctor holding stethoscope to pregnant woman's stomach

Chorionic villus sampling: All you need to know

Chorionic villus sampling (CVS) is a test performed in the first trimester, usually 10-12 weeks, that can identify more than 200 chromosomal abnormalities in the fetus. It is typically used in mothers over 35, when there is a family history of a certain genetic abnormality, or your healthcare provider suspects a developmental issue based on the ultrasound or a previous test. The chorionic villi, which project from the placenta, allow transfer of nutrients and oxygen from mother to baby and contain the fetus’s genetic makeup.

CVS Procedure

You may be asked to drink liquids before the test, since it is easier for the practitioner if you have a full bladder. The chorionic villi sample can be obtained with a thin catheter via the cervix or the abdomen. You will receive local anaesthetic on your belly if it is the latter, which could sting a bit, and both methods may cause some cramping when the sample is taken. The procedure is guided by an ultrasound so that the biopsy is taken from the right area. There are very few risks associated with the procedure, and the chance of experiencing complications such as infection, amniotic fluid leakage, or miscarriage is about 1%. You might see some spotting or cramping for 1 or 2 days after the procedure, which is normal. You will probably get results in 1-2 weeks.

What it tests for

Some of the common chromosomal or genetic abnormalities CVS can detect are down syndrome, Tay-Sachs disease, sickle-cell disease, cystic fibrosis, and hemophilia, a disorder affecting blood clotting. Amniocentesis, a test that can be performed later than CVS, tests for neural tube defects as well, and might be used if your CVS results are inconclusive. CVS is 99% accurate in paternity testing, and is often used to compare the fetal DNA to that of the potential father.

Overall, the benefits of CVS often outweigh the risks. If you have a high-risk pregnancy or would prefer to have advanced notice of developmental problems, talk to your healthcare provider about performing the test.

Reviewed by Dr. Jamie Lo
Read more
  • Mayo Clinic Staff. “Chorionic Villus Sampling.” Mayo Clinic. Mayo Clinic, 10/17/2015. Web.
  • C White. “Chorionic villus sampling.” U.S National Library of Medicine. MedlinePlus, 11/16/2014. Web.

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