Foetal screening defects missed2nd June 2008
Scientists in Italy say that the tests and scans currently used in pregnancy are only picking up about half of genetic abnormalities in foetuses.
Only half of potential chromosomal abnormalities were being spotted by tests, a European genetics conference was told. The team presenting their findings said women needed more information about the limitations of testing, and about the risks involved.
Tests involving an amniocentesis - which takes a sample of the amniotic fluid surrounding the baby - can cause miscarriage, for example.
The test, which is used to predict the best-known example of chromosomal defects: Down's syndrome, will cause one in 100 women who have it to miscarry.
Down's syndrome produces development problems, a higher rate of heart defects and a characteristic facial appearance in babies, although people with Down's syndrome can live past 50 with modern support in place.
An amniocentesis can also show if the foetus has other chromosomal defects like Edward's syndrome and Patau syndrome.
Lead researcher Francesca Grati, of Italy's TOMA Laboratory in Busto Arsizio, found that in 100,000 pre-natal invasive tests like amniocentesis, only around half of the abnormalities present in the samples had been correctly identified.
She told the European Society of Human Genetics conference in Barcelona that there were many other defects which had not been picked up by these tests, and that the tests did not even detect 100% of common abnormalities.
She called for routine counselling to be given to patients about the limitations of screening methods and the risks posed by invasive testing methods like amniocentesis.
Experts said it made more sense to focus testing on a small number of the most common birth defects, leaving aside potentially stress-causing information about the rarest conditions.
A spokeswoman for the Royal College of Midwives said women were unlikely to be able to absorb the implications of around 50 different possible conditions, some of which had as low as a one in 150,000 chance of happening.
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