All pregnant women are offered screening tests, such as scans and/or blood tests, to assess the chance of a chromosomal abnormality in the baby, but at present a diagnostic test is the only way to obtain definite information about a baby's chromosomes during a pregnancy.
Up-to-date information on current NHS screening programmes can be found at:
Screening tests are non-invasive and do not pose any risk to the baby but they will not give enough information to confirm whether the baby has a chromosome defect.
Invasive tests can rule out or confirm a chromosome abnormality but carry a risk of miscarriage for up to three weeks after the test. In twin or multiple pregnancies invasive tests can show if each baby has normal chromosomes.
Genetics is the study of human cells, and a Clinical Geneticist will interpret the results of chromosome tests taken from blood, skin, bone marrow, or connective tissue. When tests during pregnancy have shown a chromosome abnormality the clinical geneticist, if consulted, will discuss the results with the family.