Safe: The new blood test can be used in the ninth week of pregnancy and has so far proved to be 100 per cent accurate
A blood test for pregnant women that can detect Down’s syndrome without the risk of miscarriage has been developed. It can be used in the ninth week of pregnancy – far earlier than existing methods – and has so far proved to be 100 per cent accurate. Scientists believe the procedure could also prevent hundreds of unborn babies being lost through miscarriages.
About 30,000 women deemed at high risk of carrying a Down’s baby face the dilemma of whether or not to undergo tests each year. Currently they are offered a nuchal fold test, which uses ultrasound screening to measure fluid at the back of the foetus’s neck at 11 weeks.
Other existing methods for detecting the condition – which causes physical and learning disabilities and raises the risk of heart disease – are amniocentesis, in which a needle is inserted into the womb to remove amniotic fluid, and chorionic villus sampling, whereby a piece of placenta is taken for genetic testing. Infants with the condition have three copies of the Chromosome 21 instead of the normal two.
However, the checks can cause miscarriage in between one in 100 and one in 200 cases. The U.S. scientists behind the new blood test hope that it will be available on the NHS within the next five years. But they are also confident women will be able to pay for it privately even sooner, at a cost of around £750.
Scientists believe the test could prevent hundreds of unborn babies being lost through miscarriage
The test works by looking at a normal sample of a woman’s blood taken from her arm and analysing the DNA of the foetus. This is present in a woman’s bloodstream just a few weeks into the pregnancy. Scientists then look for abnormalities in the baby’s chromosomes – sections of DNA – which cause Down’s and other genetic disorders, including Turner syndrome and Klinefelter’s syndrome. At present, the screening methods for detecting Down’s and other conditions can be highly unreliable. Many women undergoing the initial ultrasound are wrongly told their baby is healthy only to later discover it has a disorder.
Scientists believe the test could prevent hundreds of unborn babies being lost through miscarriage The new test has been designed by scientists from the genetic- testing firm Natera working alongside academics from Colombia University, New York. Jonathan Sheena, chief technology officer at Natera, said: ‘At the moment pregnant women are presented with a really poor choice. ‘They can either undergo a safe but pretty unreliable test to tell if they are carrying a foetus with an abnormality. Or they can go through an uncomfortable, invasive and risky procedure. ‘What we’re trying to do is give mothers the best information possible. We’re trying to eliminate surprise. We want pregnant mothers to do whatever they can to prepare.’
Early trials of the test, which were presented to the American Society for Reproductive Medicine’s conference in San Diego, show that it has been 100 per cent accurate. It has been tried on 148 women and in all cases was correctly able to detect any abnormalities. In recent years several other groups of scientists have announced that they are also developing similar tests. But according to these researchers, this latest check is far more accurate. It can also look for twice as many abnormalities including genetic disorders that lead to learning difficulties.
Women who discover their baby has one of these conditions will then be offered counselling. Depending on the condition, some may decide to undergo a termination. Presently around 1,100 cases of Down’s syndrome are diagnosed in pregnancy each year, with around 90 per cent of women opting to have an abortion. For the test to be available on the NHS it would have to be approved by the National Institute for Health and Clinical Excellence, the National Health Service’s rationing body. But the scientists are increasingly hopeful that it will be given the green light and will become available for patients within the next five years.
Daily Mail UK