Scientists working on a Down's Syndrome test that poses no risk to the unborn baby have published promising results.
At present, pregnant women at high risk of carrying a Down's syndrome baby may be offered diagnostic tests, including amniocentesis or chorionic villus sampling (CVS).
These involve removing tissue or fluid from the womb to check for abnormalities in the growing foetus.
But the procedures carry risks of miscarriage, leading scientists to search out new ways of collecting samples.
Researchers in Maryland in the US have been working on a non-invasive test, where blood is taken from the mother and analysed for genetic abnormalities in the child.
They extracted foetal DNA from the blood samples of 60 pregnant women and checked them for variations in the DNA sequence.
Babies with Down's Syndrome have an extra copy of chromosome 21 in their DNA, trisomy 21.
Of the 60 samples tested by the researchers, the technique correctly identified the number of chromosomes in 58 of them.
One case of trisomy 21 was not identified while one normal sample was incorrectly identified as trisomy 21.
The authors, who published their findings in The Lancet medical journal, said: "The copy number of chromosomes of interest can be directly established from maternal plasma.
"Such a non-invasive prenatal test could provide a useful complement to currently used screening techniques."
However, they added, further research was needed to improve the technique.
Source: Press Association, 02/02/2007
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