The Endometrial Microbiome and Its Influence on Implantation and IVF Success: A Systematic Review

To evaluate contemporary evidence (2020–2025) on the relationship between the endometrial microbiome and implantation outcomes in IVF, and to assess how microbial composition particularly Lactobacillus dominance versus dysbiosis affects clinical pregnancy and live birth rates.

A systematic search of PubMed, Embase, Scopus, and Cochrane Library was conducted for studies published from January 2020 to January 2025 using predefined keywords (“endometrial microbiome,” “implantation,” “IVF,” “reproductive microbiota”). Eligible studies included human IVF cycles utilizing molecular sequencing (NGS or 16S rRNA) with reported implantation, clinical pregnancy, or live birth outcomes. Non-human studies, vaginal-only microbiome analyses, and articles lacking clinical outcomes were excluded. Seventeen studies met inclusion criteria. Due to heterogeneity in sampling methods, sequencing depth, and microbiome dominance thresholds, a structured qualitative synthesis was performed.

Across reviewed studies, a Lactobacillus-dominant microbiome (>80%) was consistently associated with higher implantation rates (44–62%), improved clinical pregnancy rates (48–66%), and increased live birth rates (34–55%). Conversely, endometrial dysbiosis characterized by increased Gardnerella, Atopobium, Streptococcus, and other non-Lactobacillus species was linked to implantation rates as low as 8–20% and significantly reduced clinical pregnancy outcomes. Several 2022–2024 studies reported a two- to threefold increase in implantation failure among dysbiotic patients. Emerging evidence also suggests microbiome imbalance may impair immune-endometrial signaling and endometrial receptivity. Limited interventional studies showed that targeted antibiotherapy or probiotic restoration improved implantation in selected patients, though standardized protocols are lacking.

Evidence from 2020–2025 indicates that the endometrial microbiome is a critical and under-recognized determinant of implantation and IVF success. Lactobacillus dominance supports favorable reproductive outcomes, while dysbiosis is strongly associated with implantation failure and early pregnancy loss. These findings position the endometrial microbiome as a promising diagnostic and therapeutic target in modern reproductive medicine, emphasizing its potential role in individualized IVF treatment strategies.