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Hormonal contraception and HIV risk: A review
Results from past research studies have investigated a possible relationship between hormonal contraceptive use and HIV acquisition, but understanding remained poor due to inconsistent results and shortfalls in study design.1 A 2007 multinational prospective cohort study found no overall statistically significant association between the use of combined oral contraceptive (COC) pills or depot medroxyprogesterone acetate (DMPA) and HIV acquisition.2
A total of 6,109 women participated in the study: 2,235 in Uganda, 2,296 in Zimbabwe, and 1,578 in Thailand. All were family planning clinic clients. At the time of enrollment, the women were using no hormonal contraception, or they had used COCs or DMPA for at least three months before the study began. Women who were not using hormonal contraception used such methods as condoms alone, diaphragms and spermicides, sterilization, withdrawal, or periodic abstinence, or they used no birth control method.
In the study, the women were offered their choice of oral contraceptives or DMPA, as well as condoms. Researchers counseled women on how to use their chosen methods, as well as how to reduce their risk of HIV infection. Women also were examined for sexually transmitted infections and offered treatment if needed. HIV tests were administered four to five times a year for 15 to 24 months.
By the study's end, 213 African women had become infected with HIV, while only four Thai women were identified with the infection. Since there were too few Thai cases for a valid statistical interpretation, the researchers excluded them from the final analysis.
The researchers report that neither COCs [hazard ratio (HR), 0.99; 95% confidence interval (CI), 0.69-1.42] nor DMPA (HR, 1.25; 95% CI, 0.89-1.78) was associated with risk of HIV acquisition overall, including among participants with cervical or vaginal infections. While absolute risk of HIV acquisition was higher among participants who were seropositive for herpes simplex virus 2 (HSV-2) than in those seronegative at enrollment, among the HSV-2-seronegative participants, both combined pill users (HR, 2.85; 95% CI, 1.39-5.82) and DMPA users (HR, 3.97; 95% CI, 1.98-8.00) had an increased risk of HIV acquisition compared with the nonhormonal group.
The subgroup of women who were not infected with genital herpes at enrollment comprised about half the women in the study. Among this subgroup, those women who used hormonal contraceptive methods had an increased HIV infection risk, as shown in the statistics above: Combined pill users had almost three times and DMPA users had four times the risk of acquiring HIV when compared to women not using hormonal contraceptives.
"Among women who are HSV-2-negative, DMPA and COC users may be at increased risk of HIV acquisition," concluded the researchers in their analysis. "Additional research should confirm and interpret this finding."
Neither the World Health Organization nor the International Planned Parenthood Federation, which reviewed the study results, plans at this time to change guidelines for hormonal contraceptive use.1
Counsel on condoms
Researchers continue to look at linkages between combined pill use and increased sexually transmitted infection (STI) risk. Findings suggest that combined pills influence transcription of natural antimicrobials in the human endometrium, which may increase a woman's vulnerability to upper-tract chlamydia or HIV infection.3
In the same vein, DMPA provides no protection against STIs, including HIV. Several observational studies have shown an association between DMPA use and acquisition of chlamydia.4-6 In two studies, DMPA use has been inconsistently associated with acquisition of gonorrhea.4,6 Studies in high-risk populations, including sex workers in Kenya and Thailand, have demonstrated an association between DMPA and HIV acquisition,7,8 while other research has not observed an association.9
What does this mean for family planning clinicians? Because hormonal contraception does not protect against HIV, women who use hormonal contraception and are at elevated risk of acquiring HIV also should use condoms consistently and correctly with each sexual act if they are not in a mutually monogamous relationship with an uninfected partner.1 Advice from the current edition of Contraceptive Technology says it best: "To reduce risks for STIs, women should choose to be sexually active with one uninfected, monogamous partner or, at a minimum, use latex or polyurethane condoms with every act of vaginal or rectal intercourse and should consider condom use with oral-genital contact, too."10