Reproductive tract microbiome and therapeutics of infertility Original paper

What was reviewed?

This comprehensive narrative review explores the human reproductive tract microbiome and its significance in infertility and reproductive outcomes. It synthesizes recent research on microbial communities inhabiting both female and male reproductive systems, highlighting the use of next-generation sequencing techniques to characterize these microbiota. The review delves into the role of specific microbial taxa, particularly Lactobacillus species, and their influence on reproductive tract health, the success of assisted reproductive technologies (ART), and the pathogenesis of infertility-related disorders. It also discusses the impact of microbial dysbiosis on conditions such as bacterial vaginosis (BV), chronic endometritis (CE), endometriosis, and adverse pregnancy outcomes, including preterm birth and preeclampsia. The therapeutic potential of antibiotics and probiotics for restoring reproductive tract eubiosis and improving fertility outcomes is critically evaluated.

Who was reviewed?

The review encompasses a wide spectrum of studies involving women and men of reproductive age, with a focus on both fertile and infertile populations. It draws on data from healthy individuals, infertility patients (including those undergoing ART such as IVF), and individuals with specific gynecological or obstetric pathologies. The populations studied span various ethnicities and geographic backgrounds, as inferred from referenced multicenter and international studies. The review also includes evidence from both cross-sectional and longitudinal research, as well as meta-analyses, providing a broad perspective on microbial associations across reproductive health and disease states.

Most important findings

The review highlights that the reproductive tract harbors a complex microbiome, with Lactobacillus species dominating in healthy females and contributing to an acidic, protective environment. Dysbiosis is strongly linked to BV, infertility, adverse ART outcomes, and pregnancy complications such as preterm birth and preeclampsia. In males, seminal microbiota composition (notably the presence of Lactobacillus vs. Anaerococcus, Pseudomonas, or Prevotella) correlates with sperm quality. The endometrial and follicular microbiomes, though less studied, also appear to influence implantation success and embryo development. The presence of pathogenic or dysbiotic communities in the reproductive tract can impair fertilization, implantation, and pregnancy maintenance, potentially resulting in ART failure or reduced live birth rates. Importantly, the review discusses how biofilm formation and the three-dimensional structure of microbial communities may shield pathogens from host immune responses and antimicrobial interventions, complicating treatment.

Key implications

This review underscores the emerging clinical importance of assessing and modulating the reproductive tract microbiome in infertility management. For clinicians, it emphasizes that microbial profiling, especially using sequencing-based methods, can identify dysbiosis not detectable by standard cultures, and may inform personalized interventions. The dominance of beneficial Lactobacillus strains is associated with higher fertility and ART success, while dysbiotic states predict poorer outcomes. Probiotic therapies and targeted antibiotics show promise but require further validation; indiscriminate antibiotic use may disrupt beneficial microbes. Future directions include integrating microbiome analysis into reproductive health assessments and developing microbiota-based therapeutics to optimize reproductive outcomes. A nuanced understanding of microbial signatures could enable precision medicine approaches in infertility and pregnancy care.