The research – led by Professor Kypros Nicolaides and his team at King’s College Hospital and King’s College London – is published in the Ultrasound in Obstetrics and Gynaecology journal today (Monday 26 October).
In the NHS study, of those pregnant women judged to be at high risk for carrying a baby with Down’s syndrome, a far greater number opted for the ‘cell-free’ DNA test compared to those requesting invasive testing. 60 per cent of women in the study chose the cell-free DNA test, compared to 38 per cent opting for invasive testing.
At present, a woman’s risk of carrying a baby with Down’s syndrome is based on an assessment of her age, the level of hormones in her blood and the results of a ‘nuchal scan’, which measures fluid collection at the unborn baby’s neck.
Women deemed to be high risk following this ‘combined assessment’ are given the option of further tests, which involve using a needle to take a sample of the placenta (chorionic villous sampling, or CVS) or the fluid that surrounds the baby (amniocentesis). CVS or amniocentesis are still the only tests that can provide a definitive diagnosis of Down’s syndrome, but both carry a risk of miscarriage.
The study involved 11,692 women with single pregnancies treated at two different NHS hospitals; King’s College Hospital, London, and the Medway Maritime Hospital, Kent. A small proportion of these women (395) were found to be at high-risk for Down’s syndrome.
The cell-free DNA test – which involves a far less-invasive blood test of the pregnant woman – is a highly reliable test for Down’s syndrome, but is currently only available privately and costs hundreds of pounds.
The results of the study suggest that the best approach to screening for Down’s syndrome is to continue to offer the combined test to all pregnant women, as is standard currently, but to begin offering the cell-free DNA test to all women judged to be at an increased risk.
As well as showing the cell-free DNA test is the preferred option for pregnant women, the study also provides evidence that the test can be easily incorporated into routine clinical care within the NHS. Introducing the cell-free DNA test on the NHS would lead to a higher proportion of affected pregnancies being identified, resulting in a small increase in the overall cost to the NHS, but a major decrease in invasive tests.
Crucially, the study also showed that although Down’s syndrome could be detected in more babies, this did not translate into a higher number of pregnancy terminations. Many women want to know if their baby is affected so that they can make an informed decision for themselves and their family.
Professor Kypros Nicolaides, Director of the Harris Birthright Research Centre for Fetal Medicine at King’s College Hospital, and Professor of Fetal Medicine at King’s College London, said: ‘Our research puts the case for offering the cell-free DNA test on the NHS. This would improve the performance of screening, and reduce the number of unnecessary invasive tests and miscarriages.’
King’s College Hospital and King’s College London are both part of King’s Health Partners Academic Health Sciences Centre, a pioneering collaboration between the hospital and university, as well as Guy’s and St Thomas’ and South London and Maudsley NHS Foundation Trusts.
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King’s Health Partners Academic Health Sciences Centre (AHSC) is a pioneering collaboration between King’s College London, and Guy’s and St Thomas’, King’s College Hospital and South London and Maudsley NHS Foundation Trusts.
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