A new non-invasive test for pregnant women worried that their unborn child has Down's syndrome has been developed by scientists.
The technique involves looking for tell-tale chromosome fragments in a blood sample.
It allowed scientists to pinpoint signs of chromosomal abnormality in 18 pregnant women.
Last year the US company Ravgen announced the successful trial of a similar detection method.
At present a procedure called amniocentesis is used to test for chromosomal abnormalities. This involves inserting a long needle through the mother's abdomen and drawing off fluid from the womb.
As well as being uncomfortable and inconvenient, amniocentesis carries a small risk of miscarriage or infection.
Down's syndrome occurs when a foetus has three copies of chromosome 21 instead of two.
The problem is an example of aneuploidy, or having an abnormal number of chromosomes.
Professor Stephen Quake, from Stanford University, California, who led the new study, said: "Non-invasive testing will be much safer than current approaches.
"The earlier you know you've got a foetus with Down syndrome, the better able you are to prepare. The research is reported in the journal Proceedings of the National Academy of Sciences.
