SCIENTISTS in Hong Kong claim to have developed a new risk-free test for Down's syndrome in unborn children which would save hundreds of pregnancies a year.
Based on a simple blood sample taken from an expectant mother, the new test would enable doctors to examine a foetus's chromosomes without performing invasive procedures, which carry a high risk of inducing miscarriage.
At present, the only way of
diagnosing the condition in an unborn child involves inserting a needle into the womb and taking a sample of either the amniotic fluid around the foetus or the placenta. This is then analysed to see if there are any abnormalities in the foetal DNA.
However, the tests are extremely risky, causing miscarriage in around one in every 100 pregnancies, and leaving many couples and expectant mothers with an anguished dilemma over whether or not to take the test.
The new technique, in contrast, would require only a small sample of the mother's blood, which could be taken in a few seconds as part of a standard check-up.
New technology would then enable scientists to isolate samples of the foetus's DNA within the mother's blood, and this could then be analysed for any abnormalities.
Known as the non-invasive prenatal diagnosis test, the procedure is possible because small amounts of the foetus's DNA enter the mother's bloodstream via the placenta.
These DNA strands are shorter than those of the mother, and so can be identified, isolated and analysed.
Early research, from the Chinese University of Hong Kong, published in the Nature Medicine journal, suggests the tests have a 90% accuracy rate in identifying Down's foetuses, and a 97% success rate in identifying foetuses not affected by the condition.
More extensive trials are planned, with the aim of improving accuracy even further, and there are hopes that the new diagnostic could be available in hospitals within around five years.
Nigel Carter, who is leading a research team into the new technique at the Wellcome Trust Sanger Institute near Cambridge, said: "As well as your ultrasound scan, you would have a few millilitres of blood taken for your Down's test. It's the sort of procedure that could move from being offered only to mothers at risk to a more normal screening procedure."
Lyn Chitty, of the Great Ormond Street Hospital, agreed. She said: "This whole technology really is going to change prenatal diagnosis."
Down's syndrome affects between one in 800 and one in 1,000 pregnancies. However, it is more likely to affect children of older mothers, with the risk of having a Down's child rising significantly over the age of 40.
If the new diagnostic procedure is introduced, it would increase the likelihood of Down's testing becoming routine, saving around 340 healthy unborn children who die every year because of the current diagnostic procedure.
But there are some fears that routine Down's testing could lead to an increase in the number of abortions.
