Women who receive the so-called “birth control shot” have about 40 percent higher odds of becoming infected with HIV, compared to women using some other form of birth control or no birth control at all, researchers reported.The hormones in Depo-Provera might cause changes in the vaginal wall, alter bacteria found in the vagina, or influence a woman’s immune response — any of which could increase risk of HIV, Rlph said.It also could be that the women who use Depo-Provera may be younger, more sexually active and less likely to use condoms. “These things also place women at increased risk of HIV,” Ralph said.Future studies should focus on high-risk women who use Depo-Provera, including commercial sex workers or women who have a partner with HIV, she added.

However, the review’s authors said that the increased risk does not outweigh the contraceptive benefits of Depo-Provera, particularly in the African nations where these studies took place.

Banning Depo-Provera would leave many women in developing countries without immediate access to alternative contraceptive options, which would likely lead to more unintended pregnancies, said lead author Lauren Ralph, an epidemiologist at the University of California, Berkeley, School of Public Health.

Because childbirth remains life-threatening in many developing countries, more women could die if they lose access to Depo-Provera, she said.“The risk we observe in our study would not be enough to remove Depo from women’s contraceptive mix,” Ralph concluded.Results of the review were published online Jan. 9 in The Lancet Infectious Diseases.