Abstract
PURPOSE: The uterine microbiome of in vitro fertilization (IVF) patients was analyzed using next-generation sequencing (NGS) targeting 16S rRNA. Lactobacillus spp. were examined, with a special focus on Lactobacillus iners. The effects of antibiotic therapy on pregnancy outcomes were investigated. METHODS: A total of 257 IVF patients underwent endometrial microbiome testing. Patients were initially classified based on the percentage of Lactobacillus spp. into the Lactobacillus-dominant microbiome (LDM) group and the non-LDM group using a cutoff of 90%. Treatment was provided to non-LDM patients. Treated patients who improved on the second test were included in the Post-treatment group, and their pretreatment status was also examined. RESULTS: Lactobacillus was dominant in many IVF patients, but some patients showed Gardnerella or other bacteria associated with bacterial vaginosis. The treatment improvement rate for the non-LDM group was 81.4%, with an equivalent or better pregnancy success rate compared with the LDM group. The effect on pregnancy outcomes of Lactobacillus may differ by species, with L. crispatus and L. gasseri tending to act positively, whereas L. iners at ≥ 74.2% acts negatively. CONCLUSIONS: This study shows that the recovery of an LDM in non-LDM IVF patients improves the composition of the endometrial microbiome, and pregnancy outcomes approach those of patients initially having an LDM. Furthermore, in LDM cases, L. iners species were also associated with lower pregnancy rates. These findings suggest that both the presence and type of Lactobacillus species are important for IVF success and that targeted microbiome treatment may improve reproductive outcomes.