Effects of combined oral contraceptives, depot medroxyprogesterone acetate and the levonorgestrel-releasing intrauterine system on the vaginal microbiome.

Objectives: Prior studies suggest that the composition of the vaginal microbiome may positively or negatively affect susceptibility to sexually transmitted infections (STIs) and bacterial vaginosis (BV). Some female hormonal contraceptive methods also appear to positively or negatively influence STI transmission and BV. Therefore, changes in the vaginal microbiome that are associated with different contraceptive methods may explain, in part, effects on STI transmission and BV.

Study Design: We performed a retrospective study of 16S rRNA gene survey data of vaginal samples from a subset of participants from the Human Vaginal Microbiome Project at Virginia Commonwealth University. The subset included 682 women who reported using a single form of birth control that was condoms, combined oral contraceptives (COCs), depot medroxyprogesterone acetate (DMPA) or the levonorgestrel-releasing intrauterine system (LNG-IUS).

Results: Women using COCs [adjusted odds ratio (aOR) 0.29, 95% confidence interval (CI) 0.13-0.64] and DMPA (aOR 0.34, 95% CI 0.13-0.89), but not LNG-IUS (aOR 1.55, 95% CI 0.72-3.35), were less likely to be colonized by BV-associated bacteria relative to women who used condoms. Women using COCs (aOR 1.94, 95% CI 1.25-3.02) were more likely to be colonized by beneficial HO-producing Lactobacillus species compared with women using condoms, while women using DMPA (aOR 1.09, 95% CI 0.63-1.86) and LNG-IUS (aOR 0.74, 95% CI 0.48-1.15) were not.

Conclusions: Use of COCs is significantly associated with increased vaginal colonization by healthy lactobacilli and reduced BV-associated taxa.

Implications: COC use may positively influence gynecologic health through an increase in healthy lactobacilli and a decrease in BV-associated bacterial taxa.