Scientists have devised a blood test for expectant mothers which will predict whether their unborn child has the chromosomal abnormalities which cause Down's syndrome. The test could replace the process of invasive amniocentesis tests, which carry a risk of miscarriage and is worrying for expectant parents, within three years.
Two groups of scientists, based in America and Hong Kong, have come up with separate novel solutions to make blood tests possible.
Pregnant women have foetal DNA in their blood which could be tested for Down's syndrome. But it has so far proved difficult to distinguish between the mother's and foetus's DNA.
Research by the American scientists published in today's Lancet has identified a method to distinguish between mother and foetal DNA to count chromosomes affected by aneuploidy - the defects which cause Down's syndrome. But the technique is not yet perfect and of the 60 women sampled two were given incorrect results.
Separate research due to be published in Nature Medicine next week, seen by The Guardian, is being hailed as taking the technology one step further by identifying chromosomal abnormalities in expressions of the placental DNA circulating in the mother's blood.
This technique has now been adopted by a company in the Netherlands which is working with a European network of laboratories to do a large trial of the test.
Neil Avent, co-ordinator of the Special Non-Invasive Advances in Foetal and Neonatal Evaluation Network (SAFE), which has 50 members in 19 countries and will trial the method, said: "At the current rate it will take two to three years for the test to become available.
"We need to validate it with a larger scale study. The Hong Kong research is more revolutionary and we will be trialling it through the network of laboratories."
He added that there would be an economic argument about whether the test was cost-effective as it would initially prove more expensive than amniocentesis. "It's a no-brainer when it comes to tests for Down's syndrome. It's a non-invasive test which is much safer."
Amniocentesis is offered after 15 weeks of pregnancy in women who are considered being at higher risk of having a baby with chromosomal abnormalities because something has shown up on a scan or other tests have predicted it.
Around 20ml of amniotic fluid is extracted from the womb using a fine needle guided by ultrasound. Just over one in every 100 amniocentesis procedures is understood to cause a miscarriage though the risk largely depends on the quality of the doctor carrying out the procedure.
On average only one in every 400 pregnancies leads to a baby with Down's syndrome.
