THE AMERICAN Medical Association took a stand this week in favor of testing a French abortion pill, RU-486, in this country. The pill is used in combination with prostaglandin to terminate pregnancies of less than five weeks. It has been marketed in France, where it was used in one out of four abortions last year, but it is not yet available in the United States. It is, without doubt, both safe and effective. A study published in the New England Journal of Medicine last March traced the experience of more than 2,000 women who had used the drug. Ninety-six percent had complete abortions with no side effects. Of the remaining patients, 3 percent had to have an additional surgical procedure, and one percent had heavy bleeding. Only one woman needed a transfusion.

Why isn't the pill being marketed here? The principal reason is that the manufacturer has not yet sought approval from the Food and Drug Administration. This cannot be because the sales potential is negligible, since about 1.6 million surgical abortions are performed here each year. Population experts believe, however, that other factors have caused the developers to hesitate. There is still some uncertainty about the extent to which state legislatures will be able to limit the right to abortion, and the French -- perhaps looking at the meat-ax approach taken in legislatures such as Louisiana's -- may fear the right to abortion will be eroded and their product criminalized.

That doesn't sound like a realistic assessment of the situation -- in fact, early procedures are thought to be far less objectionable to the American public than are the understandably more controversial late-term abortions -- but it is easy to understand why foreign businessmen might hesitate in an uncertain climate. The American penchant for product liability lawsuits also worries manufacturers, especially if there is even a one-in-a-thousand chance of an unsuccessful abortion resulting in a birth defect.

Some of the more militant antiabortion forces will continue to argue against allowing the drug to be used in this country, perhaps more strongly, because it makes the procedure so private and so relatively simple as to take the steam out of the public debate. But there is a complicating factor that goes beyond abortion: scientists have found that RU-486 may be effective in improving lactation, in combating breast cancer and other hormone-related cancers and even as a birth control medication. For these reasons alone, it should be available on the American market. The strong support of the medical association should encourage the manufacturers and be influential in generating public support here.