London: US scientists have developed a new blood test for pregnant women that can detect unborn children with Down’s syndrome without the risk of miscarriage.
It can be used in the ninth week of pregnancy – far earlier than existing methods – and scientists behind it believe the procedure could also prevent hundreds of unborn babies being lost through miscarriages, the Daily Mail reported.
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 new test has been designed by scientists from the genetic- testing firm Natera working alongside academics from Colombia University, New York.
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.
And they hope that it will be available on the NHS within the next five years.
“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,” the Paper quoted Jonathan Sheena, chief technology officer at Natera, as saying.
“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,” he stated.
Early trials of the test, which were presented to the American Society for Reproductive Medicine’s conference in San Diego, showed 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.
The test 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.