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Blood test identifies Down's syndrome

A blood test for pregnant women can determine whether they are carrying a baby with Down's syndrome.

US company Ravgen Inc has developed the noninvasive test, which looks for chromosome fragments in blood samples.

At present a procedure called amniocentesis is used to test forchromosomal abnormalities. This involves inserting a long needlethrough the mother's abdomen and drawing off fluid from the womb.

As well as being uncomfortable and inconvenient, amniocentesis carries a small risk of miscarriage or infection.

Down's syndrome occurs when a fetus has three copies of chromosome 21 instead of two.

The problem is an example of aneuploidy, or having an abnormal number of chromosomes.

The new Ravgen test allowed scientists to pinpoint signs of chromosomal abnormality in 18 pregnant women.

The firm successfully trialled a similar detection method last year.

Professor Stephen Quake, from Stanford University, California, who ledthe new study, said: "Noninvasive testing will be much safer thancurrent approaches.

"The earlier you know you've got a foetus with Down's syndrome, the better able you are to prepare.

The research is reported in the journal Proceedings of the National Academy of Sciences.

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