New Down’s test may replace surgery

Scientists have developed a blood analysis that tells expectant mothers whether they are carrying a child with Down’s Syndrome and hope to offer the test to all pregnant women.

The test could replace existing surgical techniques used to diagnose the genetic disorder in unborn babies. These techniques cause about one in 100 women to miscarry. Researchers say the new test will be cheap and simple enough for doctors working in most clinics to screen any pregnant woman who requests it.

In a blind study of blood samples taken from 40 pregnant women, the test correctly identified 14 cases of Down’s Syndrome, with no false positives, though a larger clinical trial is needed to validate these results. Details of the test are described in the journal Nature Medicine.

“The advantage is that we can introduce prenatal diagnosis for Down’s Syndrome to all pregnant women and it will have no risk for the baby,” said Philippos Patsalis, who led the team at the Cyprus Institute of Neurology and Genetics in Nicosia.

“I believe that in less than two years, we can have this in clinical practice,” he said. “All pregnant women might want to carry out the test so they know if they are carrying a Down’s Syndrome pregnancy or not.”

Baby’s genetic material in mother’s bloodstream
The syndrome is caused by the presence of extra genetic material from chromosome 21, which leads to learning difficulties, heart defects and a greater risk of dementia and leukaemia in later life.

Scientists developed the test after research showed that genetic material shed by the unborn baby could be detected in the mother’s bloodstream and used to spot the extra chromosome linked to Down’s Syndrome.

The test exploits the fact that regions of chromosome 21 from the baby carry more chemical tags, known as methylation, than the mother’s DNA.

It is one of a number of tests under trial that may become a reliable means of diagnosing Down’s Syndrome as well as other genetic disorders. —

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