Chorionic Villus Sampling (CVS)

Chorionic villus sampling (CVS) is a test carried out during pregnancy to detect specific abnormalities in an unborn baby. A sample of cells is taken from the placenta (the organ that links the mother’s blood supply with her unborn baby’s) and tested for genetic defects.

CVS is an alternative to amniocentesis, where a sample of the mother’s amniotic fluid is taken for testing. CVS can be carried out earlier than amniocentesis, which is usually carried out between weeks 15 and 20 of pregnancy.

Results from amniocentesis can take two to three weeks to come through. This may mean that your pregnancy is at a more advanced stage, around 20 weeks or more, before you can consider the results.

If you are at risk of passing a genetic condition onto your child, your doctor or midwife will be able to discuss the tests with you, explain why they might be necessary, and help you and your partner make your decision.

In some cases, you may be referred to a genetic counsellor (a healthcare professional trained in genetics). They will discuss your risk of passing on certain genetic conditions and can offer you advice about what to do when you get the results of CVS.