Chorionic villus sampling
Chorionic villus sampling (CVS) is a form of prenatal diagnosis to determine genetic abnormalities in the fetus. It entails getting a sample of the chorionic villus (placental tissue) and testing it. It is generally carried out only on pregnant women over the age of 35 and those who have a higher risk of down syndrome and other chromosomal conditions.
The advantage of CVS is that it can be carried out at 10-12 weeks of pregnancy, earlier than amniocentesis (which is carried out at 15-18 weeks). However, it is more risky than amniocentesis, with a 1 in 100 to 200 risk that it will cause a miscarriage.