Professor Dennis Lo from The Chinese University of Hong Kong used cutting edge DNA technology to test the blood samples from 753 pregnant women, who were all at high risk of having a baby with Down syndrome, in Hong Kong, Britain and the Netherlands. Eighty-six of the women carried a fetus with Down syndrome.
The test results were highly accurate in detecting Down syndrome in unborn babies and did not give false negative results, Lo says.
Currently, women in high-risk groups -- often women who are older -- undergo a combination of scans and hormone level tests in order to determine if they need to have an invasive test such as amniocentesis or chorionic villus sampling, but these invasive tests can increase the risk of miscarriage, Lo explains.
The study authors conclude that the blood test could be used to accurately rule out Down syndrome among high-risk pregnancies before amniocentesis or chorionic villus sampling is considered.
Down syndrome occurs in around 1 in 800 births, with the risk much higher in older women.
The findings are published in the British Medical Journal.