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New Down’s Syndrome Test For Pregnant Women

Posted Nov 21 2008 4:28pm

Scientists have announced a new blood test that could be used to determine whether an unborn baby has Down’s syndrome.

The test has been trialled at Stanford University in the United States and looks for specific chromosome abnormalities by looking at a blood sample.

The Proceedings of the National Academy of Sciences journal, has reported that the tests carried out at Stanford University were able to identify significant signs of irregular chromosomes in 18 women as well as diagnosing nine concrete cases of Down’s syndrome.

Following the success of these trials, the institute is keen to carry out similar tests on a much larger scale. The test was also able to correctly identify two other genetical disorders. Down’s syndrome arises in a baby when there is an extra copy of chromosome 21, resulting in physical and intellectual difficulties.

If three copies of chromosome 21 are found in the baby’s blood, rather than the normal two, there is a higher risk of an increase of the chromosome in the mother’s blood, as DNA can pass from the baby to the mother via the placenta.

The so-called “Shotgun sequencing test” finds and counts these DNA fragments and can cleverly detect even the smallest increase in chromosome 21.

A rival American company, Ravgen Inc. claimed to have developed a similar test last year.

Currently, the method used for testing unborn babies for Down’s syndrome involves a process called amniocentesis. A long needle is inserted into the womb and fluids are extracted from the amniotic sac. The process is uncomfortable and invasive and in a small percentage of cases, can cause miscarriage or infection. Currently statistics show one woman in 100 will miscarry from the test - as reported by the Royal College of Obstetricians and Gynaecologists. Incidentally, only a small number of women have the test.

Professor Steven Quake who headed the Stanford trials has revealed that the tests could be taken at an even earlier stage than the current one allows. This will in turn allow women more time to make an informed choice. He says,

“Non-invasive testing will be much safer than current approaches. The earlier you know you’ve got a foetus with Down syndrome, the better able you are to prepare.”

Lyn Chitty, a genetic expert of 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 and the other major aneuploidies, trisomies 13 and 18.”

Meanwhile other scientists are seeking to discover alternative Down’s signifiers in maternal blood. Unfortunately these tests would not be able to be used on all women unlike the DNA test.

The chief executive of the Down’s Syndrome Association, Carol Boys says,

“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.”

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Tuesday, October 7th, 2008 at 5:57 pm
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