The female lower genital tract harbors a complex microbial community essential for homeostasis and health. During pregnancy, the female body undergoes unique hormonal changes that contribute to weight gain as well as modulations in immune function that can afect microbiota composition. Several studies have described the vaginal microbiota of pregnant women from the USA, Europe and Mexico. Here we expand our knowledge about the vaginal microbial communities during the third trimester to healthy expectant Brazilian mothers. Vaginal samples were collected from patients delivering at the Hospital de Clínicas de Porto Alegre, Brazil. Microbial DNA was isolated from samples and the V4 region of the 16S rRNA gene was amplifed and sequenced using the PGM Ion Torrent. Brazilian pregnant women presented three distinct types of microbial community at the time of labor. Two microbial communities, Cluster 1 and Cluster 3, presented an overall dominance of Lactobacillus while Cluster 2 tended to present higher diversity and richness, with the presence of Pseudomonas, Prevotella and other vaginosis related bacteria. About half of the Brazilian mothers sampled here had dominance of L. iners. The proportion of mothers without dominance of any Lactobacillus was higher in Brazil (22%) compared to UK (2.4%) and USA, where this community type was not detected. The vaginal microbiota showed signifcant correlation with the composition of the babies’ gut microbiota (p-value=0.002 with a R2 of 15.8%). Mothers presenting diferent vaginal microbiota shared diferent microorganisms with their newborns, which would refect on initial colonizers of the developing newborns’ gut
