Howard Hughes Medical Institute researchers have developed a new prenatal blood test that accurately detected Down syndrome and two other serious chromosomal defects in a small study of 18 pregnant women. If confirmed in larger trials, they say, the test would offer a safer and faster alternative to invasive prenatal tests such as amniocentesis that pose a small risk of miscarriage.
Researchers have long known that a pregnant woman's blood contains small amounts of DNA from the fetus. Howard Hughes Medical Institute researcher Stephen R. Quake and colleagues at Stanford University devised an ingenious way to the scan fetal DNA present in the mother's blood to determine whether the fetus' cells contain extra chromosomes associated with several types of severe birth detects.
The test developed by Quake's team was more accurate than techniques used in previous efforts to diagnose aneuploidy by analyzing fetal DNA. Aneuploidy occurs when there are either too many or too few chromosomes in cells. Down syndrome, for example, is caused by a trisomy -- three copies instead of two -- of chromosome 21.
"We believe this is the first demonstration of a universal, noninvasive test for Down and other aneuploidies," said Quake, senior author of the research article, which was published online in the early edition of the Proceedings of the National Academy of Sciences (PNAS) on October 6, 2008. "We need a larger clinical study to understand a bit more about the best way to implement it, but I am highly optimistic it will be used as a diagnostic test in short order."
Amniocentesis and chorionic villus sampling (CVS), which are currently considered the "gold standard" in prenatal testing, involve sampling cells in amniotic fluid. Those cells are obtained by inserting a needle into the mother's uterus. The procedure carries up to a one percent risk of inducing a miscarriage. For that reason, routine use of these invasive diagnostic tests has largely been li
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Howard Hughes Medical Institute