The decision by Health and Human Services Secretary Kathleen Sebelius means the Plan B One-Step emergency contraceptive will remain behind pharmacy counters, as it is sold today -- available without a prescription only to those 17 and older who can prove their age.
The Food and Drug Administration was preparing to lift the age limit on Wednesday and allow younger teens, who today must get a prescription, to buy it without restriction. That would have made Plan B the nation's first over-the-counter emergency contraceptive, a pill that can prevent pregnancy if taken soon enough after unprotected sex.
But Sebelius intervened at the eleventh hour and overruled FDA, deciding that young girls shouldn't be able to buy the pill on their own -- especially since some girls as young as 11 are physically capable of bearing children.
"It is common knowledge that there are significant cognitive and behavioral differences between older adolescent girls and the youngest girls of reproductive age," Sebelius said. "I do not believe enough data were presented to support the application to make Plan B One-Step available over the counter for all girls of reproductive age."
The move will anger a pivotal part of Obama's Democratic base, and Sen. Patty Murray of Washington, a member of the Senate leadership, quickly asked for Sebelius to explain her decision. But the decision also could help Democrats make their case to independents, whose support will be critical in next fall's presidential election, that Obama is not the liberal ideologue Republicans claim.
Wednesday's decision followed Obama administration reversals this year on some environmental and other issues that irked Democrats.
It was the latest twist in a nearly decade-long push for easier access to emergency contraception, and the development shocked women's groups and maker Teva Pharmaceuticals, which had been gearing up for over-the-counter sales to begin by month's end.
"We are outraged that this administration has let politics trump science," said Kirsten Moore of the Reproductive Health Technologies Project, an advocacy group. "There is no rationale for this move."
"This decision is stunning. I had come to believe that the FDA would be allowed to make decisions based on science and the public's health," said Susan Wood of George Washington University, who served as the FDA's top women's health official until resigning in 2005 to protest delays in deciding Plan B's fate. She said, "Sadly, once again, FDA has been over-ruled and not allowed to do its job."
But the decision pleased conservative critics of the proposal.
"Take the politics out of it and it's a decision that reflects the concerns that many parents in America have," said Wendy Wright, an evangelical Christian activist who has helped lead the opposition to Plan B.
"This is the right decision based on a lack of scientific evidence that it's safe to allow minors access to this drug, much less over the counter," said Sen. Charles Grassley, R-Iowa.
Major doctors' groups and contraception advocates say quicker access to morning-after pills could cut the nation's high number of unplanned pregnancies, but they have said they didn't expect that selling Plan B over the counter would prompt much more use by younger girls. For one thing, the pill costs about $50.
They argued that putting the pill next to the condoms and spermicides would increase access for more sexually active ages who normally browse those aisles and would learn about emergency contraception. Teva planned ad campaigns aimed at 18- to 30-year-olds.
"I don't think 11-year-olds go into Rite Aid and buy anything," said Dr. Cora Breuner of the American Academy of Pediatrics. "We want it to be available to both girls and boys who have made a serious error in having unprotected sex and should be able to respond to that kind of lack of judgment in a way that is timely as opposed to having to suffer permanent consequences."
FDA Commissioner Dr. Margaret Hamburg made clear that the decision was highly unusual. She said her agency's drug safety experts had carefully considered the question of young girls, and that she had agreed that Plan B's age limit should be lifted.
"There is adequate and reasonable, well-supported and science-based evidence that Plan B One-Step is safe and effective and should be approved for nonprescription use for all females of child-bearing potential," Hamburg wrote.
Part of FDA's consideration was a Teva-funded study that tracked 11- to 17-year-olds who came to clinics seeking emergency contraception. Nearly 90 percent of them used the pill safely and correctly without professional guidance, said company Vice President Amy Niemann. However, Teva wouldn't say how many of the youngest girls were part of the study.
"We commend the FDA for making the recommendation ... and we are disappointed that at this late date, the Department of Health and Human Services has come to a different conclusion," the company said in a statement. It was determining next steps.
Already, the FDA's age limits have gone to court. In 2009, a federal judge said the agency had set them initially based on politics, not science, and ordered the agency to reconsider. A hearing was scheduled for next week to consider whether the FDA should be held in contempt of court for not doing so earlier.
Plan B One-Step is a single pill that contains a higher dose of the female progestin hormone that is in regular birth control pills. Taking it within 72 hours of rape, condom failure or just forgetting regular contraception can cut the chances of pregnancy by up to 89 percent. But it works best within the first 24 hours. There are two other emergency contraception pills, a generic version named Next Choice that is sold like Plan B and a prescription-only pill named ella.
If a woman already is pregnant, the pill has no effect. It prevents ovulation or fertilization of an egg. According to the medical definition, pregnancy doesn't begin until a fertilized egg implants itself into the wall of the uterus. Still, some critics say Plan B is the equivalent of an abortion pill because it may be able to prevent a fertilized egg from attaching to the uterus.
Associated Press writer Ricardo Alonso-Zaldivar contributed to this report.