Plain language summary
Approximately 1 in 8 couples receive infertility services in their lifetime. However, despite the increasing usage of in vitro fertilisation (IVF) technologies, the success rate, as measured using live birth rates, is just <50% in women <35 years of age. A low-diversity, Lactobacillus-dominated microbiome in the female reproductive tract has been thought to be a sign of optimal reproductive health, whereas an increased microbial diversity has been shown to be associated with poorer reproductive outcomes. The aims of this study were to (a) explore the effect of prophylactic azithromycin treatment on the vaginal bacterial microbiome longitudinally throughout an IVF cycle and (b) determine whether the characteristics of the vaginal bacterial communities are associated with clinical outcomes. This study is an a priori prospective exploratory cohort study conducted as a part of an ongoing randomized, controlled noninferiority trial. Subjects in the parent trial were randomly assigned to an azithromycin group or no-azithromycin group. The female subjects of the parent trial who were aged between 18–43 years and undergoing the first IVF cycle with a fresh embryo transfer were eligible for this study (n=27). Results show that in vaginal microbiome samples taken at the time of egg retrieval and embryo transfer, changes in the taxonomic composition, alpha diversity, and beta diversity are not associated with azithromycin [antibiotic] exposure at the time of gonadotropin initiation. Furthermore, bacterial community structures at baseline are not predictive of those at the time of embryo transfer. Authors conclude that their findings highlight the importance of timing in the assessment of vaginal microbiome to determine its associations with reproductive outcomes.
Abstract
OBJECTIVE To determine whether prophylactic azithromycin is associated with the vaginal bacterial microbiome and clinical outcomes in subfertile women undergoing in vitro fertilization (IVF). DESIGN Prospective exploratory cohort study. SETTING Single academic fertility center. PATIENTS Subfertile women aged 18-43 years undergoing their first IVF cycle and fresh embryo transfer. INTERVENTION Primary exposure to prophylactic azithromycin (1 g orally) once at baseline. MAIN OUTCOME MEASURES The primary outcome was the effect of azithromycin on the vaginal microbiome compared with a no-azithromycin group at 3 time points throughout the IVF cycle (baseline, retrieval, and embryo transfer). The secondary outcomes were associations of vaginal bacterial communities with clinical outcomes. RESULTS A planned a priori exploratory cohort of 27 subjects (12 in the azithromycin treatment group and 15 in the no-azithromycin group) contributed 79 vaginal swabs for the analysis as part of an ongoing randomized, controlled noninferiority trial. No specific taxa were associated with azithromycin or pregnancy at any time point. Azithromycin did not affect alpha diversity or community stability. Although there were trends of a lower bacterial load and higher percentage of Lactobacillus species in the azithromycin group at the time of transfer, these were not statistically significant. In women who did not become pregnant, the percentage of Lactobacillus species was lower (P = .048; Hodges-Lehmann estimate of difference, 0.41; 95% confidence interval, 0.08-0.65) and the change in community composition over time was higher. The percentage of Lactobacillus species at baseline was not predictive of the percentage of Lactobacillus species at the time of embryo transfer. CONCLUSIONS Prophylactic azithromycin at baseline is not associated with changes in vaginal bacterial communities. Bacterial community features at the time of embryo transfer are associated with pregnancy. Bacterial community structures at baseline are not predictive of those at the time of embryo transfer. CLINICAL TRIAL REGISTRATION NUMBER NCT03386227.
Methodological quality
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