a fetal monitoring technique in which a sample of chorionic villus is extracted through the cervix or abdomen under ultrasound visualization. The earliest recommended time for sampling is the ninth week of pregnancy. The cells so obtained are subjected to chromosomal and biochemical studies to determine if any abnormalities are present in the fetus. This enables the prenatal diagnosis of such congenital disorders as Down's syndrome and thalassaemia.
Medical dictionary. 2011.