Analysis of Vaginal and Endometrial Microbiota Communities in Infertile Women With a History of Repeated Implantation Failure

Abstract Background: Repeated implantation failure (RIF) is estimated to occur in 15%–20% of infertile women undergoing in vitro fertilization-embryo transfer (IVF-ET). Molecular identification recently confirmed that the uterine microbiota may have implications for reproductive and obstetrical outcomes. One hundred forty-five women who had been diagnosed with RIF were enrolled in the study. Twenty-one healthy women were also enrolled as controls. We investigated their vaginal and endometrial microbiotas using 16S rRNA gene sequencing and compared the microbiota profiles in the patients with RIF and controls.Results: The endometrial microbiotas had higher α-diversities than did the vaginal microbiotas (p<0.001 in both patients with RIF and healthy women). The microbiota profiles showed that vaginal and endometrial samples in patients with RIF had significantly higher levels of 5 and 14 bacterial genera, respectively, than those in healthy women. These genera included Atopobium, Gardnerella, Prevotella and Megasphaera. Vaginal Lactobacillus rates in patients with RIF were significantly lower at 76.4 ± 38.9% compared with those of the controls at 91.8 ± 22.7% (p=0.018), but endometrial Lactobacillus rates did not significantly differ between the RIF patients and controls (56.2 ± 36.4% and 58.8 ± 37.0%, respectively, p=0.79) Conclusions: Impaired microbiota communities containing specific bacteria in both the endometrium and vagina were associated with implantation failure. The Lactobacillus rate in the vagina, but not the endometrium, may be a biomarker for RIF.Trial registration: UMIN Clinical Trials Registry, UMIN000031731, Registered 15 March 2018; https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000036121