DMPA, OCs and risk of STIs

Katharine McCarthy, MPH

Depo-medroxyprogesterone acetate (DMPA) and oral contraceptives (OCs) reduce risk of trichomoniasis, according to results of a systematic review.

The review in the journal Sexually Transmitted Diseases also concluded that injectable use of DMPA reduced incidence of trichomoniasis by a magnitude of 0.35 (95% CI: 0.12 - 1.01) to 0.70 (95% CI: 0.50 - 1.0), “although some of these results were not statistically significant,” said lead author Katharine McCarthy, MPH, a doctoral student at City University of New York (CUNY) Graduate School of Public Health and Health Policy in New York City.

While a body of evidence suggests that DMPA increases risk of HIV acquisition, the potential association of hormonal contraceptives with other sexually transmitted infections (STIs) has not been reviewed since 2008, according to McCarthy. 

“At the same time, initiatives such as Family Planning 2020 seek to reduce unmet family planning needs of 120 million women globally by 2020, in part through expanding access to hormonal contraceptives,” she said. 

High STI prevalence settings embracing these initiatives may have implications for STI incidence.

The investigators searched PubMed and EMBASE to identify peer-reviewed, prospective studies published between January 2009 and June 2017 that compared risk of various STIs among women using hormonal contraception versus non-hormonal methods or no methods. 

Of the 30 included studies, 25 were longitudinal cohort studies, four were secondary analysis of a randomized controlled trials and one used a nested case-control design. 

In addition, most of the participants were of reproductive age, and one-third of the studies enrolled populations considered at increased risk for an STI.

“A few studies show that DMPA likely doubles the risk of herpes simplex virus type 2 (HSV-2),” McCarthy told Contemporary OB/GYN. “However, there was inconclusive evidence that DMPA is linked to human papillomavirus (HPV), chlamydia, gonorrhea or syphilis.”

McCarthy and her colleagues were surprised that they were only able to identify a low number of prospective studies that examined the association between hormonal contraceptive use and STI acquisition. 

“In particular, few studies evaluated HSV-2 and syphilis incidence,” McCarthy said. “We also found few or no studies that examined highly effective forms of contraception such as implant, levonorgestrel intrauterine device (IUD), NuvaRing or the patch.”

Regardless, based on the substantial evidence that HSV-2 increases risk of HIV infection, and if the finding that DMPA increases risk of HSV-2 is substantiated in other prospective studies, “this could be a mechanism for the association between DMPA use and HIV acquisition.” McCarthy said. “Considering these results, appropriate family planning counseling weighing the risks and benefits of hormonal contraception use, given individual factors and regional STI/HIV prevalence, is critical to ensure informed reproductive choice.”

Moreover, the review findings are comparable to studies in mice which demonstrate heightened susceptibility of HSV-2 following prolonged treatment of more than 2 weeks with DMPA.

“Our review highlights an urgent research agenda going forward,” Ms. McCarthy said. “If large-scale prospective studies of HIV risk among women also incorporated well-measured contraceptive use, including the class of drug, and STI outcomes, it would help address noted research gaps.”

The review also underscores the continued need for counseling on the use of hormonal contraceptives and development of new hormonal methods to simultaneously address STI/HIV risk.