Hormonal Contraceptives and the Acquisition of Sexually Transmitted Infections: An Updated Systematic Review.

BACKGROUND: Evidence suggests that some forms of hormonal contraception (HC) increase women's risk of non-human immunodeficiency virus sexually transmitted infections (STIs), yet evidence has not been reviewed since 2008. We conducted an updated systematic review to incorporate studies published between January 2009 and June 2017 to examine the relationship between HCs and incident or recurrent STIs.
METHODS: We searched PubMed and EMBASE to identify prospective studies comparing risk of Chlamydia trachomatis, Neisseria gonorrhoeae, human papillomavirus (HPV), herpes simplex virus type 2 (HSV-2), Treponema pallidum, or Trichomonas vaginalis, between women using HC versus nonhormonal methods or no methods. We summarize results by type of STI and HC and study quality using an adapted Newcastle-Ottawa Quality Assessment Scale.
RESULTS: Thirty articles met the inclusion criteria. Depo-medroxyprogesterone acetate (DMPA) reduces the risk of trichomoniasis (consistent evidence) and may increase the risk of HSV-2 (strong effect, few studies); inconclusive evidence exists for HPV, chlamydia, gonorrhea, and syphilis. Data on oral contraceptive pills (OCPs; generally not differentiated whether combined or progestin-only pills) suggest that use is associated with a reduced risk of trichomoniasis with inconclusive findings for HSV-2, HPV, chlamydia, gonorrhea, and syphilis. Very few studies included norethisterone enanthate (Net-En) injectable, implants or the levonorgestrel intrauterine device.
CONCLUSIONS: Depo-medroxyprogesterone acetate and OCPs reduce the risk of trichomoniasis and DMPA may increase the risk of HSV-2. However, the potential for confounding cannot be ruled out. Future studies should specify the type of injectable or OCP used to increase understanding of biological pathways; more research is needed on implants and hormonal intrauterine devices.