Chorionic villus sampling (CVS)

CVS is done at around 11 weeks to test for Down's syndrome or other genetic or chromosomal abnormalities. A fine tube is passed into the uterus to remove some of the cells from the tissue that surrounds the baby. The cells are then tested, and the results are usually known within one to two weeks.

The advantage of CVS is that if the baby is found to have a problem and you want a termination it can be done early in pregnancy.

However, there is a slightly higher risk of miscarriage with CVS than with amniocentesis.