Influence of Intramuscular Depot Medroxyprogesterone Acetate Initiation on Vaginal Microbiota in the Postpartum Period

Abstract 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 swab samples were collected from postpartum Kenyan women initiating DMPA-IM or nonhormonal contraception (non-HC). Bacterial vaginosis was assessed by Nugent score (Nugent-BV) and bacterial community composition was evaluated using broad-range 16S ribosomal RNA gene polymerase chain reaction with high-throughput sequencing. Changes in Nugent score, alpha diversity (Shannon diversity index), and total bacterial load between contraceptive groups from enrollment to 3 months after initiation were estimated using multivariable linear mixed effects regression. Results Among 54 human immunodeficiency virus–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 (change, −1.89; 95% confidence interval [CI], −3.53 to −.25; P = .02) while alpha diversity remained stable (0.03; −.24 to .30; P = .83). Conversely, Nugent score remained relatively stable among non-HC users (change, −0.73; 95% CI, −2.18 to .73; P = .33) while alpha diversity decreased (−0.34; −.67 to −.001; P = .05). The 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 per swab sample; 95% CI, −1.19 to −.08; P = .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 it decreased significantly among women using non-HC. Choice of contraception may influence Lactobacillus recovery in postpartum women. Postpartum initiation of intramuscular depot medroxyprogesterone acetate (DMPA-IM) was not associated with change in vaginal bacterial diversity despite association with reduction in bacterial vaginosis assessed by Nugent score. DMPA-IM may delay postpartum Lactobacillus recovery compared with nonhormonal contraception.