A high-ranking Food and Drug Administration (search) official resigned Wednesday in protest of the agency's refusal to allow over-the-counter sales of emergency contraception.

Susan Wood (search), director of FDA's Office of Women's Health (search), announced her resignation in an e-mail to colleagues at the agency. The e-mail was released by contraception advocates.

The FDA on Friday postponed indefinitely its decision on whether to allow the morning-after pill (search), called Plan B, to sell without a prescription. The agency said it was safe for adults to use without a doctor's guidance but said young teenagers still needed a prescription and that it couldn't determine how to enforce an age limit — a decision contrary to the advice of its own scientific advisers.

"I can no longer serve as staff when scientific and clinical evidence, fully evaluated and recommended for approval by the professional staff here, has been overruled," wrote Wood, who also was assistant commissioner for women's health. "The recent decision announced by the Commissioner about emergency contraception, which continues to limit women's access to a product that would reduce unintended pregnancies and reduce abortions, is contrary to my core commitment to improving and advancing women's health."

Wood, a biologist, joined FDA's women's health office in 2000, after directing women's health programs at its parent agency, the Department of Health and Human Services. She has worked as a research scientist and a prominent congressional adviser.

FDA spokeswoman Suzanne Trevino did not immediately comment on the resignation.

The morning-after pill is a high dose of regular birth control that, taken within 72 hours of unprotected sex, can lower the risk of pregnancy by up to 89 percent.

Plan B's maker has been trying for two years to begin nonprescription sales, and the FDA's latest postponement was a surprise: Commissioner Lester Crawford won Senate confirmation to take his job only after promising members of Congress to make a final decision by Sept. 1.

Crawford announced Friday that the agency considered over-the-counter sales to women 17 and older fine, but that he would open for 60 days of public comment the question of how to enforce an age limit or even if FDA could authorize simultaneous prescription and nonprescription sales. He would not say how soon FDA would rule.

Plan B opponents, who consider the drug tantamount to abortion and have intensely lobbied the Bush administration to reject over-the-counter sales, praised Crawford's move, saying easier access to emergency contraception may encourage teen sex.

But contraception advocates called Friday's action a case of politics trumping science, saying easier access to the pills could halve the nation's 3 million annual unintended pregnancies. FDA's scientists say the pills are safe, used by more than 2.4 million Americans and millions more women abroad with few side effects, and in December 2003 the agency's scientific advisers overwhelmingly backed over-the-counter sales for all ages.

FDA rejected that recommendation, citing concern about young teens' use of the pills without a doctor's guidance. Maker Barr Pharmaceuticals reapplied, asking that women 16 and older be allowed to buy Plan B without a prescription while younger teens continue to get a doctor's note — saying an age limit could be enforced just as it is for sales of cigarettes.

The drug has no effect if a woman already is pregnant. It works by blocking ovulation or fertilization, or possibly by interfering with implantation of a fertilized egg into the uterus, the medical definition of pregnancy.