Prenatal diagnosis - An earlier look at baby's genes

Tests based on fetal DNA circulating in a woman's blood are expected to replace invasive prenatal tests, such as amniocentesis, that are typically done later in pregnancy and pose a small risk of miscarriage. Researchers have already used fetal DNA from maternal blood to successfully test for genes that cause diseases such as cystic fibrosis, Huntington's disease, or the blood disorder thalassemia. So far the tests have only been able to detect mutations passed onby the father. The techniques are now being refined to address bigger challenges, such as identifying Down syndrome. However, earlier fetal DNA testing will raise ethical questions.