A new study has revealed that women who use a certain type of injectable birth control are at a higher risk of becoming infected with HIV than those who take the pill.
A large meta-analysis of 12 studies in sub-Saharan Africa showed that the use of the contraceptive, depot medroxyprogesterone acetate (DMPA), increases the risk of acquiring HIV by moderately 40% compared with women using non-hormonal methods and those not practicing birth control.
The increased risk was slightly lower, 31 percent, among women in the general population than those already at higher HIV risk. The contraceptive, depot medroxyprogesterone acetate, is sold under the brand name Depo-Provera, and it is administered as a shot every three months. The researchers selected the studies based upon methodological rigor, such as whether they accounted for the use of condoms.
In addition to Depo-Provera, the studies also examined other commonly prescribed forms of hormonal contraception, such as the injectable norethisterone oenanthate (sold as NET-EN), combined oral contraceptives and progestin-only pills. The other birth control methods did not appear to increase HIV infection risk for women in the general population.
Study’s lead author Lauren Ralph of UC Berkeley, said that the results had potentially broad implications because hormonal contraceptives remain popular for women worldwide. Approximately 144 million women worldwide use hormonal contraception, and of those about 41 million women use injectable forms of birth control instead of the pill. It remains unclear why the increased risk was seen among those using Depo-Provera but not the other forms of hormonal contraception, the authors said.
One possibility may be that birth control with higher levels of progestin, the synthetic form of the natural hormone progesterone, changed the vaginal lining or altered local immunity, increasing the risk for HIV infection, though the researchers emphasized that this study did not examine the physiological effects of the different contraceptive methods and more research on potential underlying biologic mechanisms is needed.
The researchers cautioned that the increased HIV infection risk needs to be considered in the context of the risks associated with not using birth control. The researchers noted that the results highlight the need for more studies among high-risk populations. Among the 12 studies analyzed, only two included sex workers or women with HIV-positive partners.