Is the test used to detect Down’s too risky?
Risks in testing unborn babies for Down's syndrome are far higher than previously claimed, new research will say this week.
For every three unborn Down's syndrome babies prevented from being born, two healthy babies will be miscarried because of the methods used to detect the condition.
The research claims that, in detecting and preventing the birth of 660 Down's babies, 400 healthy foetuses are lost.
The research casts doubt on the advice and risk assessment given to women when they are deciding whether to undergo the screening and subsequent testing to assess the health of an unborn baby.
The National Health Service currently cites a miscarriage rate of between 1 and 2% following the invasive amniocentesis and chorionic villus sampling (CVS) tests, which are offered to expectant mothers who are considered to be "at risk" after they have been screened.
The authors of the paper - which is being published in the Down's Syndrome Research and Practice journal - say that, while the number of pregnancies diagnosed with Down's syndrome that are terminated, miscarried or born are recorded, no analysis has ever been attempted to determine the number of non-Down's babies lost.
To detect as many Down's babies as possible, the initial screening threshold is set wide, which means that more than 95% of women defined as "high risk" will not be carrying a baby with the disorder, yet most go on to have the amniocentesis or CVS tests.
About 750 Down's babies are born every year in England and Wales and the Department of Health said the primary aim of screening for the syndrome was to help women make informed decisions about their pregnancies.
The National Institute for Health and Clinical Evidence has recommended a new "combined screen", which is meant to be more effective in assessing who is at risk, but this has yet to be rolled out nationally.
The Down's charity has now written to the government asking for a thorough reappraisal of the "purpose, performance and safety" of the screening programme.
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