Down syndrome, characterized by varying degrees of intellectual impairment and distinguishing facial features, as well as other internal maladies that often contribute to a shortened life expectancy, is caused by carrying three copies (trisomy) of chromosome 21 instead of two. While in the general population it affects one in every 600 babies born, the rate significantly increases to one in every 385 births for pregnant women who are 35, and the incidence continues to rise as a woman ages. Currently, about one in 10 women opt to undergo either amniocentesis or chorionic villus sampling — two invasive procedures that carry a one to two percent chance of miscarriage — in order to diagnose the ailment. But now, an experimental new blood test that screens for a gene mutation associated with Down syndrome eliminates the risk of miscarriage and can diagnose Down syndrome by the eleventh week of pregnancy.
Published in Nature Medicine, researchers from the Cyprus Institute of Neurology and Genetics in Nicosia sampled blood from pregnant women and mothers of Down syndrome and healthy babies, identifying with 100 percent accuracy 14 Down syndrome cases and 26 normal fetuses.
“This is an important study because more and more women are having children at a later age when the risk of Down syndrome increases significantly,” notes ACSH staffer Jonathan Leaf.
Though intrigued by the results, ACSH's Dr. Gilbert Ross expresses his skepticism. “This very small study is a paradigm of a hypothesis-generating study. The new blood test appears to have a 100 percent predictive value, but I would like to see a larger study investigating the success rate of this diagnostic tool.”
