London: Researchers have developed a blood test for pregnant women that can detect Down's syndrome in unborn babies without the risk of miscarriage.
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, the Daily Mail reported.
Down's syndrome is a chromosomal condition that can cause physical and learning disabilities and also raise the risk of heart disease.
Scientists believe the test could prevent hundreds of unborn babies being lost through miscarriage.
The current detection tests for the condition can cause miscarriage in between one in 100 and one in 200 cases.
The new 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.
The new test has been designed by scientists from the genetic-testing firm Natera working alongside academics from Colombia University, New York.
"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," Jonathan Sheena, chief technology officer at Natera, said.
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.
The test can also look for twice as many abnormalities including genetic disorders that lead to learning difficulties.