During pregnancy, a woman’s uterus houses and protects a developing fetus for about nine months. Within the uterus, the fetus is surrounded by a sac called the chorionic membrane. Special cells extend from this membrane into the placenta; these cells are called chorionic villi. Chorionic villi cells have the same genetic makeup as the growing fetus and can be analyzed to identify genetic and chromosomal abnormalities. This procedure is called chorionic villus sampling, or simply CVS.

The placenta can be in several different locations within the uterus. Therefore, an ultrasound is performed to locate the placenta and determine the best approach for the procedure. A catheter is then guided through the vagina and cervix to the placenta. With suction from the catheter, a small piece of the placenta is gently removed. The chorionic cells are sent to a laboratory for examination, and final test results can be expected in one to 2 weeks.