Safe: The new blood test can be used in the ninth week of pregnancy and has so far proved to be 100 per cent accurate
A blood test for pregnant women that can detect Down’s syndrome without the
risk of miscarriage has been developed. It can be used in the ninth week of
pregnancy – far earlier than existing methods – and has so far proved to
be 100 per cent accurate. Scientists believe the procedure could also prevent
hundreds of unborn babies being lost through miscarriages.
About 30,000 women deemed at high risk of carrying a Down’s baby face
the dilemma of whether or not to undergo tests each year. Currently they are
offered a nuchal fold test, which uses ultrasound screening to measure fluid at
the back of the foetus’s neck at 11 weeks.
Other existing methods for detecting the condition – which causes
physical and learning disabilities and raises the risk of heart disease –
are amniocentesis, in which a needle is inserted into the womb to remove
amniotic fluid, and chorionic villus sampling, whereby a piece of
placenta is taken for genetic testing. Infants with the condition have three
copies of the Chromosome 21 instead of the normal two.
However, the checks can cause miscarriage in between one in 100 and one
in 200 cases. The U.S. scientists behind the new blood test hope that it will
be available on the NHS within the next five years. But they are also confident women will be able
to pay for it privately even sooner, at a cost of around £750.
Scientists believe the test could prevent hundreds of unborn babies being lost through miscarriage
The test works by looking at a normal sample of a woman’s blood taken
from her arm and analysing the DNA of the foetus. This is present in a woman’s
bloodstream just a few weeks into the pregnancy. Scientists then look for
abnormalities in the baby’s chromosomes – sections of DNA – which cause
Down’s and other genetic disorders, including Turner syndrome and Klinefelter’s
syndrome. At present, the screening methods for detecting Down’s and
other conditions can be highly unreliable. Many women undergoing the
initial ultrasound are wrongly told their baby is healthy only to later
discover it has a disorder.
Scientists believe the test could prevent hundreds of unborn babies
being lost through miscarriage The new test has been designed by scientists
from the genetic- testing firm Natera working alongside academics from Colombia
University, New York. Jonathan Sheena, chief technology officer at Natera,
said: ‘At the moment pregnant women are presented with a really poor choice. ‘They
can either undergo a safe but pretty unreliable test to tell if they are
carrying a foetus with an abnormality. Or they can go through an uncomfortable,
invasive and risky procedure. ‘What we’re trying to do is give mothers the best information possible.
We’re trying to eliminate surprise. We want pregnant mothers to do whatever
they can to prepare.’
Early trials of the test, which were presented to the American Society
for Reproductive Medicine’s conference in San Diego, show that it has been 100
per cent accurate. It has been tried on 148 women and in all cases was
correctly able to detect any abnormalities. In recent years several other
groups of scientists have announced that they are also developing similar
tests. But according to these researchers, this latest check is far more
accurate. It can also look for twice as many abnormalities including genetic
disorders that lead to learning difficulties.
Women who discover their baby has one of these conditions will then be
offered counselling. Depending on the condition, some may decide to undergo a
termination.
Presently around 1,100 cases of Down’s syndrome are diagnosed in
pregnancy each year, with around 90 per cent of women opting to have an
abortion. For the test to be available on the NHS it would have to be approved
by the National Institute for Health and Clinical Excellence, the National
Health Service’s rationing body. But the scientists are increasingly hopeful
that it will be given the green light and will become available for
patients within the next five years.
Daily Mail UK
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