According to a new research from the Harris Birthright Research Centre for Fetal Medicine at King’s College London in England published in journal Ultrasound in Obstetrics & Gynecology, routine screening during the first trimester using a non-invasive blood test that analyzes fetal DNA can accurately detect Down’s syndrome and other genetic fetal abnormalities. The results of this study suggest that the test is safer than the currently available screening strategies (such as the risk-posing amniocentesis) and could potentially change current standards in prenatal testing.
Current screening for Down’s syndrome (also called trisomy 21) and other trisomy conditions includes a combined test done between the 11th and 13th weeks of pregnancy, and involves an ultrasound screen and a hormonal analysis of the pregnant woman’s blood. However, only chorionic villus sampling and amniocentesis can identify and dismiss fetal genetic abnormalities with absolute certainty. Both of these tests carry a risk of miscarriage since they are invasive to the fetus.
Although there have been several previous studies indicating that non-invasive prenatal diagnosis for trisomy syndromes using fetal cell free (cf) DNA from a pregnant woman’s blood is potentially a very reliable alternative to current screenings, this study led by doctor Kypros Nicolaides, MD is the first to demonstrate its feasibility and accuracy. Testing conducted in about a thousand pregnancies at 10 weeks had a lower false positive rate and higher sensitivity for fetal trisomy than the combined test done at 12 weeks of pregnancy. As authors of this study explain: “This study has shown that the main advantage of cfDNA testing, compared with the combined test, is the substantial reduction in false positive rate. Another major advantage of cfDNA testing is the reporting of results as very high or very low risk, which makes it easier for parents to decide in favor of or against invasive testing,”