What is CVS (chorionic vilous sampling)?

Alexander Kofinas M.D.

CVS is a procedure by which we obtain a small amount of tissue from the fetal placenta in order to test the baby' chromosomes in patients who are at risk of having a baby with Down syndrome or other genetic abnormalities. CVS is the safest procedure available at 12 weeks and the only procedure that can be performed safely before 16 weeks gestation. CVS has been shown to be as safe or safer than amniocentesis, which can only be performed at 16 weeks or later. The procedure involves the insertion of a 20-gauge needle through the abdominal wall and 3-4 mg of placental tissue is removed. The size of the needle is the same as that used for an amniocentesis. CVS was originally conducted through the vagina. This method is not as safe as the trans-abdominal approach and most clinicians have abandoned it in favor of the abdominal one. The risk of pregnancy loss because of the procedure is approximately 1 in 300.