Doctors who conducted a survey of 200 English health authorities and Scottish boards say the introduction of the test is patchy. They want a centrally funded, nationally organised scheme which could double the number of detections of Down's pregnancies.
The call for a national approach comes as a woman in north London, Michelle Huberman, plans to sue her obstetrician for not telling her about the test. According to reports in yesterday's newspapers, Ms Huberman, 34, gave birth to a Down's baby, Annalie, seven months ago.
At the time the test was not widely available and because of her age Ms Huberman would not have been in a high risk category for a Down's baby. But she argues that if she had been given information about the test she could have made her own decision.
Ms Huberman chose to have her ante-natal care and delivery at a private hospital which charges between pounds 179 and pounds 300 a day for a room. She says she loves her baby but would have had an abortion if Down's had been diagnosed during her pregnancy.
She is now reported to be appealing against a decision to refuse her legal aid to fund a claim for pounds 1m in damages.
Her case raises important issues over the range of screening tests offered to pregnant women - and how soon a test should be offered after its 'discovery'.
Ten days ago Professor Nick Wald and colleagues from St Bartholomew's hospital, London, who devised the screening method, published results of a three-year study of 12,000 women which proved the efficacy of the method.
The test, first conducted about four years ago, is a means of assessing a pregnant woman's risk of carrying a Down's baby using a simple blood test and computing the measurements of levels of three substances in the blood.
As an assessment of risk only, it is not foolproof and detects about half the at-risk pregnancies. Even so the new method, called the Bart's triple test, detected 12 out of 25 Down's pregnancies compared to 7 using old methods.
If the computer analysis shows that a pregnant woman has a
1 in 250 chance of Down's syndrome she is offered amniocentisis, a sampling of the amniotic fluid which at about 18 weeks will detect Down's syndrome. As the risk of Down's syndrome increases with the age of the mother from about 1 in 2,000 at age of 20, to about 1 in 20 at 45, health authorities offer amniocentisis to women over 37. Amniocentitis carries a risk of spontaneous abortion.
Three-quarters of Down's babies, however, are born to women under 37 - as the majority of babies are born to younger women. The important point of the new test is that it is offered to all pregnant women, whatever their age, so that amniocentisis is only offered to those at greatest risk and the risk of losing the baby can be avoided.
One disquieting aspect of Professor Wald's survey of health authorities was that 12 of them did not seem to understand his screening method. In a letter in the current edition of the Lancet he says that 12 authorities indicated that they plan to offer the screening method only to older women.
'Such screening will have the unfortunate effect of missing affected pregnancies in these older women without detecting affected pregnancies in younger women who could be shown to be at high risk,' he said. 'The policy is inequitable and such a step-wise approach is best avoided. Screening would be improved if it were funded and organised as a national public health service.'
Leading article, page 18Reuse content