Non-invasive test for prenatal diagnosis

A new non-invasive test that examines fetal DNA can pick up genetic abnormalities such as Down's syndrome and, unlike more intrusive tests that may raise the risk of miscarriage, it poses no threat to the mother or fetus. Right now there is no test available that can reliably do what has been done in this study, which is, to determine whether a baby has a genetic abnormality or not, without any invasive procedure. In a study of 60 pregnant women, researchers from the York Hospital, New York, USA, described that the test used fetal DNA extracted from blood samples taken from the mother to screen for chromosomal abnormalities and showed promising results. It was found that the blood test correctly diagnosed Down's syndrome, one of the most common genetic abnormalities, in two cases. It also produced a false positive and a false negative. Down's syndrome occurs when the fetus has three copies of chromosome 21 instead of two. The risk of having a Down's syndrome baby increases with maternal age. The test can be adapted to look for abnormalities in any chromosome or single gene disorders. Women 35 years or older have been advised to have genetic testing for Down's syndrome and other disorders. But recently it has been recommended that all women be given the option of having genetic testing. Standard tests to detect Down's syndrome include amniocentesis and chorionic villus sampling, which is performed in the first 13 weeks of pregnancy, analyses placenta cells to detect any genetic abnormalities. Amniocentesis is usually done at about 16 weeks and involves inserting a needle to withdraw a small amount of amniotic fluid. The new test detects genetic abnormalities in the fetus by looking at single nucleotide polymorphisms, which are small mutations in DNA. Though the results are encouraging, but larger studies need to be done. The test is promising and opens a new era in prenatal diagnosis but to be optimally used as a routine prenatal screening or diagnostic test, their findings need to be replicated in a larger trial.