Endometrial Microbial Network Organization Is Associated with Implantation Success Following Single Euploid Embryo Transfer

The role of the endometrial microbiome in embryo implantation remains incompletely understood. While most studies have focused on taxonomic composition and Lactobacillus dominance, the ecological organization of microbial communities associated with implantation success has received limited attention. The aim of this study was to investigate whether implantation outcome following euploid embryo transfer is associated with differences in endometrial microbial network structure and community organization. Endometrial biopsies collected during the window of implantation from 95 women undergoing subsequent euploid embryo transfer were analyzed using 16S rRNA gene sequencing. Microbial diversity, co-occurrence networks, community structure, hub taxa, network robustness, and microbial association patterns were evaluated. The Pregnant group demonstrated a more interconnected microbial network with a greater number of significant associations, larger ecological modules, and increased network integration than the Non-pregnant group. Seventeen microbial associations were unique to the Pregnant network, whereas eleven were unique to the Non-pregnant network, indicating implantation-associated ecological rewiring. Lactobacillus-centered association patterns also differed between groups. These findings suggest that successful implantation is associated with coordinated endometrial microbial community organization rather than changes in individual taxa. Microbial network structure may represent a novel dimension of endometrial receptivity assessment.