New Safe Downs Syndrome Test

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New Safe Downs Syndrome Test
Scientists have developed a new, safer blood test that can tell if an unborn baby has Down's syndrome.

Amniocentesis, which is currently used, is an invasive procedure which risks miscarriage and damage to the foetus. A Stanford University test of DNA evidence in blood from 18 pregnant women correctly identified nine cases of Down's Syndrome and the university now wants to conduct tests on a larger group.

Babies with Down's syndrome have an additional chromosome which causes physical and intellectual problems. The new test correctly identified all the chromosomal abnormalities in a specially selected sample of 18 pregnant women - nine cases of Down's syndrome and two other inherited disorders caused by an abnormal number of chromosomes.

Dr Stephen Quake and his Stanford team say they need to repeat their study with a larger number of women, but they are confident that it could be used routinely in hospitals a few years from now. He said: "Non-invasive testing will be much safer than current approaches."

Downs Syndrome is usually confirmed after an amniocentesis, in which a needle is used to take a sample of the fluid within the womb. Approximately one in 100 women who have the test will miscarry as a result, according to the Royal College of Obstetricians and Gynaecologists. Dr Quake said the new DNA test could be carried out at an earlier stage of pregnancy than the current tests, giving women more time to make choices about their pregnancy.

A similar invasive procedure that takes a tissue sample from inside the womb, called chorionic villus sampling, carries a miscarriage risk of two in 100. It can be carried out at an early stage of pregnancy than amniocentesis - after 10 weeks gestation compared with after 15 weeks for amniocentesis.

Dr Lyn Chitty, an expert in genetics and foetal medicine at University College London Hospital, said: "This is a potentially exciting development which may take us closer to a safer, non-invasive test for Down's syndrome...". She said other scientists were looking at different genetic markers in maternal blood for Down's. However, these tests would not work in all women, unlike the DNA test.

Carol Boys, chief executive of the Down's Syndrome Association, said: "There is no question that these non-invasive tests will be introduced in the next few years. It's therefore incredibly important that potential parents are given accurate information on Down's syndrome before they make a choice about whether to terminate or not. We don't consider Down's syndrome a reason for termination, but we recognise that bringing up a child with Down's syndrome isn't right for everyone. The more informed parents are, the better the position they are in to make the choice that is right for them."

October 2008

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