Elevated Risk of Bacterial Vaginosis among Users of the Copper Intrauterine Device: A Prospective Longitudinal Cohort Study

Limited evidence suggests that the non-hormonal contraceptive copper intrauterine device (Cu-IUD) may increase bacterial vaginosis (BV) risk, possibly due to increased volume and duration of menses, a common side effect of Cu-IUD use. While increases in bleeding typically resolve within 6-12 months following initiation, evaluations of the association between Cu-IUD and BV have not included more than six months of follow-up. This secondary analysis of an HIV-1 prevention trial included 2,585 African women ages 18-45 followed for up to 33 months. Women reported contraceptive use each month. BV was evaluated by Nugent score in six-monthly intervals and, if clinically indicated, by Amsel's criteria. Andersen-Gill proportional hazards models were used to (1) evaluate BV risk among Cu-IUD users relative to women using no/another non-hormonal contraceptive and (2) test changes in BV frequency before, while using, and following Cu-IUD discontinuation. BV frequency was highest among Cu-IUD users at 153.6 episodes per 100 person-years (95% CI: 145.2, 162.4). In adjusted models, Cu-IUD users experienced 1.28-fold (95% CI: 1.12, 1.46) higher BV risk relative to women using no/another non-hormonal contraception. Compared to the six months prior to initiation, BV risk was 1.52-fold (95% CI: 1.16, 2.00) higher in the first six months of Cu-IUD use and remained elevated over eighteen months of use (p