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By Jonathan Leake and Emily Milich
A TEST on pregnant women to check for Down's syndrome causes up to
four healthy babies to be miscarried for every abnormality it detects, a
study
has shown.
Amniocentesis - a procedure in which a long needle is inserted into the
womb to draw off fluid for genetic testing - is typically used when
other, less
definitive tests have shown there is a risk of Down's.
About 40,000 women a year undergo it. Only about 100 un-born babies are
confirmed with the syndrome, but the study found that up to 400 healthy
fetuses are subsequently miscarried.
Amniocentesis usually follows blood screening or ultrasound scans that
indicate a fetus may have Down's syndrome. The study examined what
happened when amniocentesis tests are carried out after ultrasound scans
alone.
It found that some of the features on ultrasound scans which doctors are
taught to identify as warning signs of Down's syndrome are misleading,
or even possibly worthless. It means that many women may be being
recommended to have amniocentesis - and run the risk of miscarriage -
unnecessarily.
Professor Rebecca Smith-Bindman, of the University of California in San
Francisco, who led the Anglo-American research team during a sabbatical
year at St Bartholomew's medical school, London, said amniocentesis,
while remaining a useful test, should be used more selectively.
"These women were recommended for amniocentesis on the basis of
ultrasound scans which relied on features that are mostly harmless to
the
baby and which almost all disappear during pregnancy," she said.
Her findings were welcomed by Professor Kypros Nicolaides, the head of
foetal medicine at King's College hospital, London, who has campaigned
against the increased use of invasive testing in pregnancy. "There
has been an explosion in invasive testing since the 1970s," he said.
"The incidence of Down's syndrome has not increased, but the number of tests has jumped
from 3,500 to 40,000 a year, with an all-too-predictable loss of
life."
About 1,000 babies are born with Down's each year in Britain. It is
caused by a chromosomal abnormality and leads to mental retardation.
Older women are at higher risk and one reason for the surge in
amniocentesis tests is a trend towards women having babies later in
life.
Many women also prefer to have amniocentesis, and accept the risk of
miscarriage, rather than risk having a baby with Down's. They are told
the
chance of miscarriage associated with amniocentesis is 1%.
A top hospital trust has been criticized for apparent discrimination
against handicapped babies who needed life-saving heart surgery.
The report of an investigation into the treatment of 49 children at the
Royal Brompton and Harefield Trust in west
London describes a catalog of
mismanagement and delays, which in some cases was followed by the
death of the child. Five families have launched medical negligence
claims.
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