Fetal Treatment Program of New England

Chorionic Villus Sampling

Chorionic villi cells are found in the placenta and contain the same genetic material as the baby’s cells: DNA, chromosomes and enzymes. Chorionic villus sampling (CVS) tests for chromosomal abnormalities and a host of other genetic disorders in a developing fetus. We recommend this test if you or your partner has a genetic disorder. CVS provides much of the same information as an amniocentesis but can be done earlier, between 10 and 12 weeks of pregnancy, and is used to find: 

  • Chromosomal defects such as Down syndrome, trisomy 13, trisomy 18, and sex chromosome abnormalities like Turner syndrome and Klinefelter syndrome (CVS is more than 99 percent accurate in diagnosing these conditions)
  • Genetic disorders such as Tay-Sachs disease, hemophilia, sickle cell disease or cystic fibrosis

How is it performed? 

Guided by ultrasound, a physician inserts a thin, flexible tube through the vagina and cervix, or through the abdomen, into the placenta to gather a sample of the chorionic villi cells. The sample is sent to a lab for genetic analysis. 

What happens afterward? 

CVA may cause some of the baby’s blood cells to enter your bloodstream. If you have Rh-negative blood, you will have blood taken before the procedure and will also receive a shot of Rhogam afterward to prevent you from producing antibodies against your baby’s blood cells. 

You may experience tenderness where the tube was inserted, minor cramping (less than a menstrual period), and some bleeding or spotting that should stop within a few days. There is a slight risk of miscarriage, infection and amniotic fluid leakage as a result of the procedure. If you experience a fever, excessive bleeding or vaginal discharge after your CVS, please call your health care provider.

What do my results mean? 

While not 100 percent accurate, a normal CVS usually means there are no signs of any genetic defects in your baby. If your CVS results are abnormal, it may be a sign of a genetic disorder. No matter your results, our genetic counselors will meet with you to carefully and completely explain your options.