An injectable birth control drug, sold under the name Depo-Provera, has been linked to a higher risk of HIV infections in women, an analysis of a number of studies in Africa suggests.
Women getting the Depo-Provera -- an injection given every 3 months -- face about a 40 percent higher risk of HIV infection compared with women utilizing other forms of birth control or not practicing birth control at all, researchers reported.
Despite the findings from data on 39,500 women in sub-Saharan Africa, the researchers emphasize that the elevated risk does not outweigh the contraceptive benefits of Depo-Provera.
"The risk we observe in our study would not be enough to remove Depo from women's contraceptive mix," says review lead author Lauren Ralph, an epidemiologist at the University of California, Berkeley.
That's particularly relevant in Africa where the reviewed studies were conducted, she says, because it could leave women in many developing countries in Africa without alternative options for contraception, increasing unintended pregnancies.
In many of those countries childbirth remains a dangerous, even life-threatening event and more women might die if they were to be without access to Depo-Provera, she concludes.
Exactly why Depo-Provera showed an increase in HIV risk when other forms of hormonal contraception did not is unclear, the researchers said, emphasizing their study did not examine the physiological effects of the different contraceptive methods.
More research on possible underlying biological mechanisms is needed, they say.
"We embarked on this study because of the inconsistency in the scientific literature on this topic," says Ralph. "The results have potentially broad implications because hormonal contraceptives remain popular for women worldwide."
Depo-Provera, or depot medroxyprogesterone acetate, is manufactured by Pfizer, which released a statement addressing the study review.
The statement said the company "is not aware of any scientific evidence showing a causal association between use of hormonal contraceptives and an increase in HIV transmission rates."
Since the studies reviews took place in Africa, they may not be strongly relevant for women in the U.S., Ralph says.
Depo-Provera is more widely used by women in Africa than in the United States where many more birth control options are readily available, she points out.
Also, the prevalence of HIV is much higher in Africa, so overall exposure is higher for women there than in the U.S., she added.
"I don't think these findings have as much relevance when we think of U.S. contraceptive policy," Ralph says.