Maternal Blood Test Can Detect Down's Syndrome in Fetus
WESTPORT, CT (Reuters Health) Nov 21--Using fluorescence in-situ hybridization (FISH), investigators from Hong Kong have been able to screen maternal blood for fetal DNA and identify fetuses with trisomy 21.
Dr. Leo L. M. Poon, and colleagues from the Chinese University of Hong Kong, Shatin, analyzed blood samples from three women carrying trisomy 21 fetuses and seven women carrying euploid [normal chromosome] fetuses. The fetal Down's syndrome diagnosis was made with amniocentesis in one patient and chorionic villus sampling (CVS) in the others.
After harvesting fetal cells from the maternal plasma, the investigators analyzed the cells using FISH with DNA probes specific for chromosomes 21, 13, 18, or Y. In a Research Letter published in the November 25th issue of The Lancet, and released early by the journal, the investigators report that all three Down's cases clearly showed three chromosome-21 signals on FISH.
The prior use of amniocentesis or CVS might increase the number of fetal cells in maternal circulation, the authors state. However, other studies have shown no difference in number of fetal cells between women who have had a prior invasive test and those who have not. Also, "fetal DNA is cleared very rapidly, with a half-life of minutes, from maternal blood."
"Our data suggest that future large-scale trials should be initiated to assess the diagnostic accuracy of this method for fetal aneuploidy [abnormal chromosome] detection. Ultimately, with further technical refinements, prenatal diagnosis by maternal plasma DNA analysis could reduce our reliance on invasive methods, leading to safer investigative protocols for mother and fetus," Dr. Poon's team concludes.
Lancet 2000;356:00-00.
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