Vaginal microbiome dysbiosis in preterm birth.

All the environmentally exposed surfaces of the human body harbor ecologically distinct microbial communities with a mutualistic beneficial relationship. Depending on the body sites, microbes may provide metabolic functions, protection against pathogens, and signaling molecules to modulate host physiology and reduce disease susceptibility. Our recent understanding of the vaginal microbiome based on culture-independent 16S rRNA gene sequencing indicates that Lactobacillus-dominated microbial communities of healthy women play an important role in decreasing susceptibility to several urogenital diseases, including bacterial, fungal and viral infections. The findings of shotgun sequencing of the vaginal microbiome suggest that microbial-derived lactic acid, bacteriostatic, bactericidal molecules, and lower vaginal pH mediate such protections and regulations. Bacterial species, the dominant component of the vaginal microbiome, also play a key role in determining the gestation period and birth outcomes of reproductive-age women. The presence of Lactobacillus crispatus species in the vaginal milieu reduces the risk of preterm delivery in women of Asian ancestry. A deeper knowledge of the vaginal microbiota's role in the succession and development of newborn gut bacteria would also be beneficial. The microbiome of the mother changes throughout pregnancy and is linked to the microbiome of the newborn. This chapter highlights updated information and new opportunities for human microbiome research, focusing on the assessment of the risk of preterm birth.