DNA tests for unborn babies now done through mother's blood at Royal London Hospital
PUBLISHED: 09:19 28 November 2017
Barts NHS trust
A new way of testing the DNA of unborn babies has been started in east London to help pregnant women get the right hospital care and avoid unnecessary jabs for antibody treatment.
Cell-free foetal DNA testing has now been tried out at the Royal London Hospital in Whitechapel to analyse babies’ blood type through a simple test on the mother’s blood.
All pregnant women until now who were blood group RhD negative had been offered ‘anti-D’ injections to prevent them forming antibodies which could cause anaemia in their unborn child in future pregnancies.
But the baby will also be RhD negative in around 40 per cent of pregnancies, which does not put women at risk of forming antibodies—so some women had been having unnecessary injections.
“This testing will help reduce unnecessary exposure of women to anti-D,” Royal London’s Haematology specialist registrar Catherine Booth said. This is a scarce resource that we must use wisely.
“It is new technology which benefits women, hospitals and the whole blood service.”
The new test allow midwives to give injections only to the women who need them. Newham and Whipps Cross hospitals are soon to follow the Royal London’s practice.
An estimated 800 pregnant women will now avoid unnecessary treatment every year, Barts Health NHS Trust has revealed this week.
The trust, which runs all three hospitals, estimates the reduced additional testing can save £30,000 a year, as there are only 15 per cent of women in Britain with blood type RhD negative with RhD negative babies.
Medical researchers have also made a breakthrough detecting more accurately serious chromosome disorders like Down’s Syndrome before birth.
They have been using DNA analysis in antenatal screening to reduce invasive testing simply by taking two blood samples at 11 weeks instead of just one.
The new method devised at Queen Mary University’s Whitechapel campus means using the second sample for more accurate “reflex DNA” screening if the first shows risk of Down’s syndrome, Edwards syndrome or Patau syndrome, and been tested at the Royal London, Newham and Whipps Cross hospitals.
Queen Mary’s Prof Sir Nicholas Wald explained: “The reflex DNA approach identified more affected pregnancies, but many fewer women are made anxious by being told they have a positive screening result.
“Reflex DNA screening is safer than conventional screening as it avoids nearly all invasive tests in unaffected pregnancies and avoids miscarriages linked to these procedures.”
The method has detected more affected pregnancies than previously, with far fewer false ‘positives’ so women don’t have to be called back just for invasive and stressful tests.
Women at present offered screening at 10 to 14 weeks with an ultrasound scan and a blood test are offered a chorionic villus sampling test if increased risk of an affected pregnancy is detected. But this involves a needle through the abdomen into the womb to collect fluid samples surrounding the foetus or placenta tissue.
The new method, instead, means two blood samples at 11 weeks, one for a conventional screening, the other for the reflex DNA test without having to recall the women for a second blood sample. It avoids unnecessary worry if a DNA test is needed, according to findings published this month in the Genetics in Medicine journal.