Diagnostic tests for Down syndrome - Chorionic villus sampling risks and benefits

Diagnostic tests for Down syndrome: These tests will give you a definite diagnosis of Down’s syndrome and sometimes other abnormalities.

Your midwife or doctor will explain what is involved and you will usually be offered counseling.

Chorionic villus sampling for Down syndrome (CVS)    

CVS can be carried out at around 11 weeks. It can give you an earlier diagnosis if you are at risk of having a child with an inherited disorder, such as cystic fibrosis, sickle cell disorder, thalassaemia or muscular dystrophy.

How Chorionic villus sampling is done

The test takes 10 to 20 minutes and may be a little uncomfortable.

Using ultrasound as a guide, a fine needle is passed through the abdomen into the uterus.

Sometimes a fine tube is passed through the vagina and cervix into the uterus instead. A tiny piece of the developing placenta, known as chorionic tissue, is taken. The chromosomes in the cells of this tissue are examined. As with amniocentesis, a rapid result can be obtained, but if all the chromosomes are going to be checked, the results may take up to two weeks.

Chorionic villus sampling risks

CVS has a 1–2% risk of miscarriage. This is slightly higher than amniocentesis.

If a test detects an abnormality

It is always difficult when you are told there is something wrong with your baby, especially if you are faced with a painful decision about the future of your pregnancy.

Your midwife or doctor will make sure you see the appropriate health professionals to help you get all the facts and support you need so you can make the choices that are right for you and your family.