SAN JOSE, Calif. • Raising the prospect of a world without birth defects, a Stanford-created blood test that can detect Down syndrome and two other major genetic defects very early in a woman's pregnancy will be available next week.

The simple blood test spares women the risk and heartache of later and more invasive tests like amniocentesis.

But it has startling social implications — heralding a not-distant future when many fetal traits, from deadly disease to hair color, are known promptly after conception when abortion is safer and simpler.

The $1,200 test, which analyzes fetal DNA in a mother who is 10 weeks pregnant, is being offered to doctors March 1 by Verinata Health, a biotechnology company in Redwood City, Calif. It licensed a technique designed by Stanford biophysicist Stephen Quake.

"It's a game changer," said Stanford University law professor Hank Greely, who studies the legal and ethical implications of emerging technologies. The controversy over abortion "is about to be hit by a tsunami of new science."

There are two converging trends, Greely said. "We've got politicians running for president who are really trying to whack away at reproductive rights at a time when the science is about to vastly expand the information that parents have about their fetus."

A similar test is already available from the San Diego company Sequenom, and at least two other San Francisco Bay area companies plan to offer noninvasive prenatal genetic testing.

The market is huge: 4.5 million U.S. births a year, of which an estimated 750,000 are "high risk," due to age or family history.

The current crop of tests only seeks major abnormalities on three chromosomes: 13, 18 and 21. They can also tell whether a fetus is a boy or girl.

But perhaps within the next five years "it seems likely that a simple blood draw from the pregnant woman will be able to provide genetic results for a fetus about not just Down syndrome," Greely said, "but cystic fibrosis, sickle cell anemia, Tay-Sachs disease and a host of other diseases."

"I don't think many parents would abort a fetus because it is blond or because it doesn't have the best genes to be an athlete," Greely said. "But I do think it will greatly increase the number of fetuses aborted for mainly medical reasons, and sometimes for nonmedical reasons, like sex because it is so much easier to find out. And you find out faster.

"You can make the decision before anyone else really knows you are pregnant — and when abortions are less complicated, medically and socially."