The risk of terminating healthy babies after a positive test for Down Syndrome is far higher than previously claimed, according to a British study. For every three unborn Down's syndrome babies aborted, two healthy babies will be miscarried because of the invasive methods used to confirm a diagnosis.

A report in the Down's Syndrome Research and Practice journal claims that for every 660 Down Syndrome foetuses which are detected and terminated in the UK each year, 400 normal children perish as well. The problem is that invasive tests are needed to confirm a diagnosis of Down Syndrome in an unborn child. These involve a small risk of miscarriage. According to the authors, Frank Buckley and Sue Buckley, of Down Syndrome Education International, the vast majority of positive blood tests for Down’s are actually false. But to confirm the diagnosis, worried mothers have an amniocentesis, a test in which amniotic fluid is extracted with a long needle. Or, earlier in the pregnancy, they can have chorionic villus sampling, in which a sample of placental tissue is taken.

The best available evidence, say the authors, suggests that the risk of pregnancy loss due to amniocentesis is 1% and that loss due to first-trimester chorionic villus sampling is 2%. Erring on the conservative side, they used a 1% loss figure for CVS in their calculations. If the more generally accepted figure of 2% is used, about 600 normal children are being unnecessarily terminated – a ratio of about 1 to 1.

The Guardian says that because the authors are Down Syndrome experts, they could be "accused of pursuing their own agenda". However, journalists seem to have cross-checked with other doctors and found no one who denied the findings. Professor Kypros Nicolaides, of King's College Hospital in London, says that it is "completely unacceptable" to lose this number of normal babies.

The Guardian also says that "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." However, at the moment, the American College of Obstetricians and Gynecologists is recommending that all pregnant women be offered prenatal screening at least before 20 weeks. In the UK, the National Institute for Health and Clinical Excellence (NICE) has recommended that all women be offered a first trimester test. ~ Guardian, Sept 14