The most popular contraceptive for women in eastern and southern Africa, a hormone shot given every three months, appears to double the risk the women will become infected with H.I.V., according to a large study published Monday. And when it is used by H.I.V.-positive women, their male partners are twice as likely to become infected than if the women had used no contraception.The findings potentially present an alarming quandary for women in Africa. Hundreds of thousands of them suffer injuries, bleeding, infections and even death in childbirth from unintended pregnancies. Finding affordable and convenient contraceptives is a pressing goal for international health authorities. But many countries where pregnancy rates are highest are also ravaged by H.I.V., the virus that causes AIDS. So the evidence suggesting that the injectable contraceptive has biological properties that may make women and men more vulnerable to H.I.V. infection is particularly troubling. Injectable hormones are very popular. About 12 million women between the ages of 15 and 49 in sub-Saharan Africa, roughly 6 percent of all women in that age group, use them. In the United States, it is 1.2 million, or 3 percent of women using contraception. While the study involved only African women, scientists said biological effects would probably be the same for all women. But they emphasized that concern was greatest in Africa because the risk of H.I.V. transmission from heterosexual sex was so much higher there than elsewhere. "The best contraception today is injectable hormonal contraception because you don't need a doctor, it's long-lasting, it enables women to control timing and spacing of birth without a lot of fuss and travel," said Isobel Coleman, director of the women and foreign policy program at the Council on Foreign Relations. "If it is now proven that these contraceptions are helping spread the AIDS epidemic, we have a major health crisis on our hands." The study, which several experts said added significant heft to previous research while still having some limitations, has prompted the World Health Organization to convene a meeting in January to consider if evidence is now strong enough to advise women that the method may increase their risk of getting or transmitting H.I.V. "We are going to be re-evaluating W.H.O.'s clinical recommendations on contraceptive use," said Mary Lyn Gaffield, an epidemiologist in the World Health Organization's department of reproductive health and research. Before the meeting, scientists will review research concerning hormonal contraceptives and women's risk of acquiring H.I.V., transmitting it to men, and the possibility (not examined in the new study) that hormonal contraceptives accelerate H.I.V.'s severity in infected women. "We want to make sure that we warn when there is a real need to warn, but at the same time we don't want to come up with a hasty judgment that would have far-reaching severe consequences for the sexual and reproductive health of women," she said. "This is a very difficult dilemma." The study, led by researchers at the University of Washington and published in The Lancet Infectious Diseases, involved 3,800 couples in Botswana, Kenya, Rwanda, South Africa, Tanzania, Uganda and Zambia. In each couple, either the man or the woman was already infected with H.I.V. Researchers followed most couples for two years, had them report their contraception methods, and tracked whether the uninfected partner contracted H.I.V. from the infected partner, said Dr. Jared Baeten, an author and an epidemiologist and infectious disease specialist. The research was presented at an international AIDS conference this summer, but has now gained traction, scientists said, with publication in a major peer-reviewed journal. The manufacturer of the branded version of the injectable, Depo-Provera, is Pfizer, which declined to comment on the study, saying officials had not yet read it. The study's authors said the injectables used by the African women were probably generic versions. The study found that women using hormonal contraception became infected at a rate of 6.61 per 100 person-years, compared with 3.78 for those not using that method. Transmission of H.I.V. to men occurred at a rate of 2.61 per 100 person-years for women using hormonal contraception compared with 1.51 for those who did not. While at least two other rigorous studies have found that injectable contraceptives increase the risk of women's acquiring H.I.V., the new research has some strengths over previous work, said Charles Morrison, senior director of clinical sciences at FHI 360, a nonprofit organization whose work includes researching the intersection of family planning and H.I.V. Source: New York Times.