Blood tests for mothers could provide diagnoses for Down鈥檚 syndrome in fetuses without the requirement to insert a long needle into the womb.
Dennis Lo, of the Chinese University of Hong Kong, found that fetal DNA isolated from the mother鈥檚 blood plasma can reveal Down鈥檚 syndrome. He says the discovery should pave the way for an effective, non-invasive test for the disorder.
Amniocentesis is the most common method of testing for Down鈥檚 syndrome but requires a long needle to take a sample of fetal cells. It carries a one per cent risk of miscarriage.
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Blood tests for Down鈥檚 syndrome are already available. But these test abnormal hormonal levels and have a success rate of only around 60 per cent.
The DNA-based test is 鈥渁 direct measure of Down鈥檚 syndrome,鈥� says Lo. 鈥淭here is no reason to think it could not be used to detect all cases.鈥�
Lo hopes the test could be used in all women. Amniocentesis is usually only recommended for women over 35, who are more likely to have a Down鈥檚 syndrome child. At age 35, the risk is one in 300. At age 45, that figure leaps to one in 28.
鈥淏ut most babies with Down鈥檚 syndrome are born to women under 35,鈥� Lo told 快猫短视频. 鈥淗opefully, this test could be used on all pregnant women.鈥�
People with Down鈥檚 syndrome carry three copies of chromosome 21, instead of the normal two. In theory, the test could be used to detect all disorders that involve abnormal numbers of chromosomes, Lo says.
Research carried out by Lo in 1997 showed that it was possible to isolate fetal cells from the mother鈥檚 blood plasma. This was previously thought to be impossible.
Now, his team has used a standard fluorescence in-situ hybridisation (FISH) test for chromosomal abnormality to detect Down鈥檚 syndrome in the fetuses of three women. Other tests confirmed the diagnosis.
鈥淚n all three cases, cells with the three chromosome 21 signals could clearly be seen,鈥� he says. The test did not detect Down鈥檚 syndrome in seven other healthy fetuses.
鈥淭hese are early days,鈥� Lo stresses. 鈥淲hat we have really done here is a proof of principle. Now we need to do tests on many more babies.鈥�
Pro-life campaigners argue that the test will mean more abortions.
But Sarah Waights of the Down鈥檚 Syndrome Association says: 鈥淧re-natal testing does not go hand-in-hand with abortion. Many people want to know whether their child has Down鈥檚 syndrome to prepare themselves to raise that child.鈥�
More at: The Lancet (vol 356, p1819)