BOSTON, OCT. 14 -- The latest version of a new prenatal screening test can reveal the genetic health of a fetus within a few hours instead of requiring several days, its developers say.

Besides being faster and simpler, they say, the test does not require the use of radioactive isotopes. This should make it easier to perform prenatal testing in poor countries where labs are not set up for complex procedures.

The researchers believe their test can frequently replace Southern blot analysis, the standard process used to check fetal DNA for inherited disorders.

"You could do a lot more of these in a week with a lot less effort than you could do Southern blot analyses. And that's going to translate into more available diagnoses," said Dr. Jane Gitschier of the University of California, San Francisco.

She successfully used the test to screen for hemophilia A, a bleeding disorder that's passed from mothers to sons. She said it also can be used to check the unborn for sickle cell anemia, Duchenne's muscular dystrophy, cystic fibrosis and a variety of other genetic diseases.

Gitschier, whose report will be published in Thursday's New England Journal of Medicine, said that, typically, the test requires five hours to perform, compared with five days for the Southern blot. She said it might also cost about one-third of the standard test, which ranges from $500 to $1,000.