Most babies are born healthy, but when a baby has a condition that is present from birth, it is called a congenital disorder. Congenital disorders can be inherited or caused by environmental factors and their impact on a child’s health and development can vary from mild to severe. A child with a congenital disorder may experience a disability or health problems throughout life.

Testing for congenital disorders can be performed from 10 weeks of pregnancy onwards. While many parents choose to have tests during pregnancy, it is not compulsory and some do not. Screening tests are designed to identify babies who do not have a congenital disorder. If a screening test does not rule out your baby having a congenital disorder, the next step is to have a diagnostic test. Diagnostic tests, such as ultrasound scans, blood tests, and sometimes urine tests, are designed to identify babies who do have a congenital disorder, and to find out what that disorder is. However, it is not possible to test for all congenital disorders during pregnancy, and testing is not perfect. Chorionic villus sampling or CVS, is usually performed between 10 to 13 weeks of pregnancy when screening tests show that your baby may have a congenital disorder. CVS can be used to diagnose babies with Down syndrome or other genetic conditions. It involves using a needle (after a local anaesthetic) to collect a small sample of cells from your placenta, which are then sent for testing.