Chorionic Villus Sampling (CVS) What It Is: Another way of
obtaining fetal tissue is to take a small amount of the
placental tissue from within the uterus, which has the same
genetic composition as the fetus. To perform a CVS test, a
needle is inserted into the placental attachment to the uterus
and a small amount of tissue is removed and sent for analysis.
The placenta can be approached either through the cervix or
through the mother's abdominal wall. When It Is Performed: This
procedure can be done at 10 to 12 weeks, which is much earlier
than routine amniocentesis. The results are available in about
five to 10 days, also much quicker than with routine
amniocentesis. The specimens obtained from this procedure can be
contaminated with maternal tissue about one percent of the time
(compared to about 0.2 percent in amniocentesis); this can
confuse interpretation of the genetic tests. There are also rare
circumstances when the abnormalities seen in the placenta may
not be present in the fetus. Not only do you n