Preterm birth (PTB) represents a leading cause of neonatal morbidity and mortality. Despite the reported association between vaginal microbiome and PTB, previous research has been inconsistent in its conclusions, and the systemic mechanisms through which the vaginal microbiome influences susceptibility to PTB remain unexplained. We set the following hypotheses: (1) analysis of the vaginal microbiome will reveal differences in the composition between Slovenian pregnant women who delivered before completed 37th week of gestation and pregnant women who delivered at term, (2) potential differences in the composition of the vaginal microbiome are associated with a specific global expression profile in maternal peripheral blood. To re-evaluate the role of the vaginal microbiome in PTB, we conducted an independent 16S sequencing study. In PTB women, we report higher microbial richness and diversity, decreased abundance of genus Lactobacillus, increased abundance of Gardnerella, and other bacterial vaginosis and aerobic vaginitis-related genera. We performed a global transcriptomic analysis of maternal whole peripheral blood to determine whether a high-risk vaginal microbiome profile (CST IV/CST III) is associated with systemic consequences. We identified several biological pathways associated with PTB (CST IV/CST III), including phosphatidylinositol signaling pathway, JAK-STAT, Fc gamma-R phagocytosis, and adherent junctions, as well as enriched diseases and functions, including inflammatory response, cell movement, granulocyte activation, phagocytosis, chemotaxis, cytoskeletal organization, and adhesion. The present study represents further evidence that the vaginal microbiome composition is associated with PTB and the possible association of risk vaginal microbiome profile with concomitant transcriptomic changes in peripheral blood. We contribute new knowledge about the potential factors leading to PTB.
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