A new, highly accurate test for Down’s syndrome has been recommended for high-risk women on the NHS.
The simple blood test is used to detect Down’s syndrome and can also pick up two other chromosomal disorders, Patau’s syndrome and Edwards’s syndrome.
The move would mean far fewer women needing invasive amniocentesis tests, which carry a 1% chance of miscarriage and around a one in 1,000 risk of serious infection.
At present, all pregnant women in England are offered a combined blood and ultrasound test when they are 10 to 14 weeks pregnant to check for abnormalities.
In new recommendations, government advisers say women found to have a one in 150 chance or greater of having a baby with Down’s, Patau’s or Edwards’s syndrome in the combined test should then be offered the new test.
The new screening method – known as non-invasive prenatal testing (NIPT) – works on the knowledge that a developing foetus’s DNA circulates in the mother’s blood.
This means some aspects of the baby’s genetic profile can be screened directly from the mother’s blood sample.
NIPT can be followed by an amniocentesis test if there is still any doubt on a diagnosis.
Ministers have yet to rubberstamp the recommendations from the UK national screening committee, but it is hoped rollout of the test could begin soon.
Studies for NIPT have shown it to be highly accurate in detecting Down’s. Researchers at Great Ormond Street hospital in London published results last year showing the test was safe, 99% accurate, and resulted in a greater number of parents taking the test.
St George’s University Hospitals NHS foundation trust has been offering the test to patients since June. Results can be turned around in five days.As part of a trial carried out at Great Ormond Street, women at high and medium risk of having a child with Down’s syndrome were offered NIPT, with more than 2,500 accepting.
Dr Anne Mackie, director of screening at Public
Health England, said: “While the evidence suggests that NIPT is much more accurate in predicting Down’s syndrome than current tests, there are a number of questions about its use in a real-life screening programme that the evidence hasn’t yet been able to clarify.
“We don’t know how good the test is for other genetic conditions – Edwards’s and Patau’s syndromes – that are currently part of the programme, and the evidence review also found that up to 13% of the NIPTs carried out didn’t give any result at all.
“The intention, therefore, is to monitor and evaluate as we go. That means rolling out the test across England in such a way that allows us to learn from the experience and alter the screening programme if necessary in light of any real-life findings.
“This will allow us to improve the information we can give women when they are offered the screening and help them make the right choice.”
In Down’s syndrome, cells carry an extra copy of chromosome 21, leading to learning difficulties which can vary from mild to severe.
In Edwards’s syndrome, there is an extra copy of chromosome 18, while babies with Patau’s syndrome have an extra copy of chromosome 13.
Most babies with Edwards’s or Patau’s syndromes die before they are born or shortly after birth. They suffer a wide range of serious problems, sometimes including major brain abnormalities.
A Department of Health spokeswoman said: “We welcome these important recommendations from the UK National Screening Committee, which have the potential to transform antenatal screening. We are now considering the recommendations.”
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