Impact of Contraceptive Choice on the Vaginal Microbiota

Abstract Purpose of Review The vaginal microbiome plays a central role in sexual and reproductive health and is increasingly recognized as a modulator of susceptibility to microbial dysbiosis (i.e. clinical- and molecular- bacterial vaginosis (BV)) and sexually transmitted infections (STIs). Contraceptive methods represent a major exogenous influence on the vaginal environment, yet their effects on microbial composition and host immunity vary by method of administration and formulation. This review synthesizes recent evidence on how hormonal and non‑hormonal contraceptive methods influence the vaginal microbiome, with emphasis on randomized controlled trials and longitudinal studies. Recent Findings Combined oral contraceptives (COC) and most systemic progestin‑only methods, including intramuscular depot medroxyprogesterone acetate (DMPA-IM) and levonorgestrel implants (LNG-implants), appear largely microbiome‑neutral, with preservation of Lactobacillus ‑dominant communities and minimal genital inflammation. Microbiome data from randomized studies for levonorgestrel intrauterine devices (LNG-IUD) remain limited, although available evidence suggests minimal disruption. In contrast, copper IUD (Cu-IUD) use is consistently associated with increased microbial diversity, depletion of Lactobacillus species and heightened inflammation. Likewise, recent evidence regarding combined contraceptive vaginal rings (CCVR) describes associations with dysbiosis and inflammatory signalling. Condoms appear microbiome‑neutral and may attenuate sex‑associated microbial perturbations, whereas spermicides are linked to epithelial disruption. Summary Contraceptive methods differentially influence vaginal microbiome composition and immune milieu in a largely method‑dependent manner. Although current evidence does not warrant changes to medical eligibility criteria, emerging microbiome insights may inform individualized contraceptive counselling, particularly for individuals with recurrent clinical-BV or elevated STI risk. Future research should prioritize long‑term, adequately powered studies integrating the microbiome, alongside immunologic and clinical outcomes.