David A. Grimes of the University of Southern California, who wrote an editorial in the journal calling the drug's "political saga" in the United States a "national disgrace," said RU-486 is a contraceptive, not an abortive agent, because pregnancy does not begin until an embryo is implanted in the uterus. "I think this will change the political landscape for this medicine," he said. "It is a use that may prevent abortion rather than cause abortion."

Half the women were given RU-486 and half got birth control pills. None of the women taking RU-486 got pregnant, compared with four pregnancies among those receiving birth-control pills. RU-486 also was less likely to cause nausea.