Influence of intramuscular depot-medroxyprogesterone acetate initiation on vaginal microbiota in the postpartum period.

Background The vaginal microbiome plays a key role in women's reproductive health. Use of exogenous hormones, such as intramuscular depot-medroxyprogesterone acetate (DMPA-IM), may alter the composition of vaginal bacterial community. Methods Vaginal swabs were collected from postpartum Kenyan women initiating DMPA-IM or non-hormonal contraception (non-HC). Bacterial vaginosis was assessed by Nugent score (Nugent-BV) and bacterial community composition was evaluated using broad-range 16S rRNA gene PCR with high-throughput sequencing. Changes in Nugent score, alpha diversity (Shannon diversity index), and total bacterial load between contraceptive groups from enrollment to three-months post-initiation were estimated using multivariable linear mixed effects regression. Results Among 54 HIV-negative women, 33 choosing DMPA-IM and 21 choosing non-HC, Nugent-BV was more common among DMPA-IM users at enrollment. At follow-up, Nugent score had decreased significantly among DMPA-IM users (Δ=-1.89 (95%CI:-3.53, -0.25; p=0.02) while alpha diversity remained stable (Δ=0.03, 95%CI:-0.24, 0.30; p=0.83). Conversely, Nugent score remained relatively stable among non-HC users (Δ=-0.73, 95%CI:-2.18, 0.73; p=0.33) while alpha diversity decreased (Δ=-0.34, 95%CI:-0.67, -0.001; p=0.05). Total bacterial load decreased slightly in DMPA-IM users and increased slightly among non-HC users, resulting in a significant difference in change between the contraceptive groups (difference=-0.64 log10 gene copies/swab, 95%CI:-1.19, -0.08; p=0.02). While significant changes in Nugent score and alpha diversity were observed within contraceptive groups, changes between groups were not significantly different. Conclusions Postpartum vaginal bacterial diversity did not change in DMPA-IM users despite a reduction in Nugent-BV, but decreased significantly among women using non-HC. Choice of contraception may influence Lactobacillus recovery in postpartum women.