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Most contraceptives not linked to HIV infection, but Depo-Provera may raise risk
Liz Highleyman, 2016-08-17 07:40:00

Birth control pills and some types of injectable and implanted contraceptives were not associated with an increased risk of HIV acquisition in an updated meta-analysis that included several recent studies, researchers reported in the August 5 online edition of AIDS. However, evidence continues to suggest that use of depot medroxyprogesterone acetate (DMPA or Depo-Provera) raises the likelihood of HIV infection. The World Health Organization (WHO) plans to meet soon to assess whether guidance needs to change in the light of the new findings.

Over the years studies have produced conflicting evidence about the link between hormonal contraception -- especially DMPA, a long-acting progesterone-only injectable -- and women's risk of becoming infected with HIV.

Chelsea Polis of the Guttmacher Institute and colleagues have conducted on-going systematic reviews and meta-analyses of studies looking at the association between contraception and HIV.

At the 2012 International AIDS Conference, Polis reported that studies to date did not show a link between oral contraceptives and HIV infection after adjusting for confounding, nor did the less widely used progesterone-only injectable norethisterone enantate (NET-EN), but a couple studies saw a significant association with DMPA.

At the 2014 conference, researchers with FHI 360 reported that an individual participant meta-analysis (analysing pooled data from all participants in multiple studies) yielded similar results, as did another meta-analysis published in the February 2015 issue of The Lancet Infectious Diseases.

For the latest updated meta-analysis, commissioned by WHO, Polis and her team searched for articles published between January 2014 and January 2016. They identified ten new studies since the last review, five of which they deemed relevant to the primary question about the link between contraceptives and HIV infection.

They again found that "the preponderance of data" for oral contraceptive pills, injectable norethisterone enanthate and levonorgestrel implants "do not suggest an association with HIV acquisition." A suggestion of increased risk with NET-EN seen in the previous review was no longer apparent. They stressed, however, that data for levonorgestrel implants are limited and there are no HIV infection data currently available for etonogestrel implants or for contraceptive patches, rings or hormonal IUDs.

They noted that the new, higher-quality studies on DMPA (or injectables considered together), which previously had mixed results in terms of statistical significance, now had hazard ratios between 1.2 and 1.7, or between a 20% and 70% increase in the risk of HIV acquisition. If the association is causal, the true magnitude of the effect is likely <1.5, they said.

"While confounding in these observational data cannot be excluded, new information increases concerns about DMPA and HIV acquisition risk in women," the study authors concluded. "Data for other hormonal contraceptive methods, including NET-EN, are largely reassuring."

"This is a critical area of research, given that hormonal contraceptives are highly effective methods for preventing unintended pregnancy and its health risks," Polis stated in a Guttmacher Institute press release. "Many places where HIV rates are high also have high levels of unmet need for contraception, unintended pregnancy, and maternal mortality. It is essential that we understand whether use of any particular hormonal contraceptive method could elevate women’s risk of HIV acquisition."

"While definitively inferring causality with observational studies is challenging, it is worth noting that the methodological quality of studies looking at the association of DMPA use with HIV acquisition in women has improved dramatically over time," she added. "This underscores the need to consider next steps on this issue carefully, in terms of clinical guidelines and further research."