Doctors' Digest

Chorionic villus sampling (CVS) – how does it work?

Early in pregnancy, the developing embryo splits into two parts: one part will eventually develop into the baby, and the other into the placenta. This vital organ supplies the baby with blood, oxygen and nutrients and removes waste for the duration of pregnancy. The part of the embryo that will become the placenta initially takes the form of small finger-shaped structures called chorionic villi. These structures probe the wall of the uterus to make contact with the mother's blood supply. Because the villi originated from the same fertilised egg as the foetus, this means they are both made up of the same genetic code (DNA) and therefore any genetic abnormalities that will be present in the baby will also be present in the villi. Chorionic villus sampling (CVS) involves taking a small selection of chorionic villus cells for genetic testing. This can reveal the presence of abnormalities that cause Down’s syndrome, cystic fibrosis, sickle cell disease, thalassaemia and other genetic (or inherited) disorders. This article on chorionic villus sampling is by Kathryn Senior, a freelance journalist who writes health, medical, biological, and pharmaceutical articles for national and international journals, newsletters and web sites.