What can the test detect?

The chorionic villus test can detect a large number of conditions, disorders and defects, including:

• Chromosomal conditions: chromosomal conditions are caused by having the wrong number of chromosomes; some disorders are characterised by having an additional chromosome, like Down’s syndrome which occurs as a result of an extra chromosome 21, while others are characterised by having too few chromosomes.
• Blood disorders: these disorders affect the carriage and manufacturing of blood cells; well known examples of blood disorders include sickle cell anaemia, which affects the way oxygen is carried around the body and thalassaemia, which affects the body’s ability to make red blood cells.
• Genetic disorders: genetic disorders, including cystic fibrosis, can be detected using the CVS test. Cystic fibrosis is an inherited disease, which is fairly common. The symptoms of cystic fibrosis can be treated but there is no specific cure.
• Musculoskeletal disorders: these disorders affect the musculoskeletal system; the most well known example is muscular dystrophy.
• Metabolic disorders: these disorders affect the absorption and digestion processes.
• Mental health conditions: conditions like fragile X syndrome, can be detected using the CVS test. This condition affects behaviour, as well as intelligence.

The CVS test cannot detect neural tube defects; neural tube defects are conditions which affect the spine and the spinal cord. The most well known example of a neural tube defect is spina bifida. The amniocentesis test can detect neural tube defects so this test may be recommended if there is a risk of the baby suffering from this condition (for example, if the ultrasound scans or blood tests have indicated abnormalities).