Chorionic villus sampling (CVS) is used to test for genetic disorders, such as Down’s syndrome, and involves taking a small sample of the chorionic villi, which are the tiny units that make up the placenta. The placenta is the organ that grows on the inner lining of your uterus (womb) through which nourishment and oxygen pass to your fetus (unborn baby). The chorionic villi have the same chromosomes as your fetus and DNA analysis will determine if your unborn child has any genetic abnormalities.

 

An ultrasound is performed to determine the age and position of the fetus and the location of the placenta. A local anaesthetic is injected into the skin, and then under ultrasound guidance a needle is passed through the abdominal wall and uterus to the placenta. Very small amounts of tissue are then drawn up into the syringe. Occasionally it is necessary to insert the needle more than once to get a sample. There is some discomfort as the needle enters the uterus.