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Thursday, 4 July, 2002, 23:23 GMT 00:23 UK
Down's screening 'won't work'
Girl with Down's syndrome
Screening for Down's syndrome is not infallible
Government plans to introduce a national screening programme for Down's syndrome will cost a fortune and still fail mothers, warn doctors.

A report in the British Medical Journal warned that a new type of screening for pregnant women would not mean a better detection of Down's syndrome babies.

They said it would also not reduce the number of women who needed a second, more risky test.

Serum screening has been routinely offered to pregnant women since the early 1990s and detects chemicals in the blood which could be a sign of Down's syndrome.


The risk goes up steeply after 35

Dr David Howe

But a team of doctors from a maternity hospital in Southampton said the serum test and nuchal fold screening were less effective than previously thought.

The test looks for differences in the appearance of the space at the back of the baby's neck, which can suggest Down's.

Risk calculation

Dr David Howe, a consultant in foetal and maternal medicine at the Princess Anne Hospital in Southampton, said the mathematical equations used to calculate women at risk did not take into account that more women were choosing to have their babies later in life.

This, he said, had led to false results.

"The modelling presumes that one in 20, over 5% of women are 35, but across most of Europe it is about 15% of women having babies over 35 and that completely changes the mathematics.

"The risk goes up steeply after 35.

"You find that 60% of babies with Down's being born to women over 35 instead of the predicted amount of 30%."

Pregnant woman
The screening programme would not be effective, warn doctors

Dr Howe said that the introduction of a national screening programme would mean a large financial outlay, but without the benefits.

He said that a unit delivering the babies of 5,000 women would expect to pay about 300,000 a year for screening.

Mr Howe's team found that areas using serum screening detected 57% of cases, those using maternal age plus serum or nuchal screening detected 52%.

But those using just a maternal age of 35 or more and anomaly scans, which look for problems at the 20-week scan, detected 54%.

Screening

A spokesperson for the Down's Syndrome Association said it was important that women were made aware of the potential pitfalls of screening.

"It is important to understand right at the beginning the fallibility of screening tests, the inherent risks involved with diagnostic tests and a little about what Down's syndrome really is before being faced with unexpected and difficult choices once testing is underway."

A spokesperson for the Department of Health said they would consider the new data before making any final decision about introducing the screening in 2004.

"Our current advice on serum screening for Down's Syndrome is based on the 1998 Health Technology Assessment report.

"This concluded that serum screening for Down's Syndrome is effective and that all women should be offered at least second trimester serum screening.

"However, we welcome any studies which could lead to improved ways of detecting Downs Syndrome.

"The UK National Screening Committee's Antenatal sub-group will consider this and other emerging research findings at its meetings this year.

"This new research will obviously be subjected to the same rigorous scrutiny which is applied to all such work."

See also:

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