Stanford University bioengineering professor Stephen R. Quake and graduate student H. Christina Fan said that most existing pre-natal tests for Down syndrome depend on a technique termed karyotyping that takes two weeks. Cells taken during amniocentesis or chorionic villus sampling are grown in laboratory culture and analyzed.

However, the new method -- a variation of the polymerase chain reaction which produces thousands of identical copies of minute samples of DNA -- produced accurate results within two hours, the researchers said.

Rapid testing alternatives exist but they are either too labor-intensive or not applicable to the whole population, Quake said.

"The technique we present in this paper can overcome these limitations," Quake said in a statement. "It is rapid and simple. We estimate that the entire procedure from sample collection to result readout would take only a few hours, substantially reducing the anxiety of the expectant parents."

The findings are scheduled to be published in the journal Analytical Chemistry.