Invasive diagnostic tests
Invasive diagnostic tests (CVS and amniocentesis) can tell you for certain if your baby has a chromosomal anomaly such as Down's syndrome. Screening tests cannot do this. They are called invasive procedures because they involve passing a very narrow needle into the body. This means CVS and amniocentesis carry a small risk of miscarriage.
The risk of miscarriage can make both deciding to have the test and actually having the procedure very worrying. Please call the ARC helpline if it would help to talk about your concerns.
Invasive diagnostic testing and twin pregnancies
Performing CVS or amniocentesis in twin pregnancies is more technically difficult and so the risk of miscarriage is higher. We strongly recommend that if you are carrying twins and planning to have an invasive test that you have it done at a specialist fetal medicine unit where the doctors will be experienced in dealing with twin pregnancies.
Non-invasive prenatal diagnosis (NIPD)
There is a great deal of research in progress internationally into using cell-free fetal DNA circulating in the mother’s blood to provide a safe prenatal test for Down’s syndrome. There is now a test commercially available in the USA. Researchers here believe it is too early to say that NIPD gives a consistently reliable diagnostic result for Down’s syndrome. Non-invasive prenatal diagnosis is not available in the UK. Professor Lyn Chitty from University College London is leading research here. For news on progress please see their research website.