Characteristics in the uterine cavity microbiota of infertile women with hydrosalpinx or endometrial polyps revealed by shotgun metagenomics

Infertility is a global public health issue, and a favorable endometrial environment is essential for successful assisted reproductive treatment. Endometrial polyps (EM) and hydrosalpinx (HD) are common gynecological disorders impairing the intrauterine milieu, but their impacts on uterine cavity microbiota remain unclear. This study enrolled 75 participants [32 fertile controls (C), 32 EM patients, 11 HD patients] to characterize their uterine cavity profiles using shotgun metagenomic sequencing. The C group showed significantly higher microbial alpha diversity than the two patient groups, with no significant difference between EM and HD groups. At the species level, EM group exhibited marked dysbiosis, characterized by elevated pathogenic bacteria, particularly Streptococcus and Streptococcus pneumoniae . HD featured a marked reduction in overall microbial load, decreased absolute abundance of core beneficial bacteria, and a relative increase in Streptococcus and Streptococcus pneumoniae . This study identifies distinct endometrial microbial profiles for EM and HD, providing novel insights into microbiota-mediated mechanisms of infertility. These subtype-specific signatures support the endometrial microbiota as a potential biomarker for infertility, offering clinical targets for antibiotic selection and therapeutic evaluation.