The Human Microbiome Project (HMP), initiated in 2007, aimed to gather comprehensive
knowledge to create a genetic and metabolic map of human-associated microorganisms
and their contribution to physiological states and predisposition to certain diseases.
Research has revealed that the human microbiome is highly diverse and exhibits significant
interpersonal variability; consequently, its exact impact on health remains unclear.
With the development of next-generation sequencing (NGS) technologies, the broad spectrum
of microbial communities has been better characterized. The lower female genital tract,
particularly the vagina, is colonized by various bacterial species, with Lactobacillus
spp. predominating. The upper female genital tract, especially the uterus, was long
considered sterile. However, recent studies have identified a distinct endometrial
microbiome. A Lactobacillus-dominated microbiome of the female genital tract is associated
with favorable reproductive outcomes, including higher success rates in natural conception
and assisted reproductive technologies (ART). Conversely, microbial imbalances, or
dysbiosis, marked by reduced Lactobacilli as well as an increased diversity and abundance
of pathogenic species (e.g., Gardnerella vaginalis or Prevotella spp.), are linked
to infertility, implantation failure, and pregnancy complications such as miscarriage
and preterm birth. Dysbiosis can impair the vaginal or endometrial mucosal barrier
and also trigger pro-inflammatory responses, disrupting essential reproductive processes
like implantation. Despite growing evidence supporting the associations between the
microbiome of the female genital tract and certain gynecological and obstetric conditions,
clear microbial biomarkers have yet to be identified, and there is no consensus on
the precise composition of a normal or healthy microbiome. The lack of standardized
protocols and biomarkers limits the routine use of microbiome screening tests. Therefore,
larger patient cohorts are needed to facilitate comparative studies and improve our
understanding of the physiological microbiome profiles of the uterus and vagina, as
well as how dysbiosis may influence clinical outcomes. Further research is required
to refine diagnostic tools and develop personalized therapeutic strategies to improve
fertility and pregnancy outcomes.
