Association between changes in salivary microbiota with glucose levels during pregnancy – findings from a pilot study

Background : Microbial shifts that correspond to host variations during pregnancy are vital in health maintenance. Significant changes have been reported in the oral microbiota of pregnant women when compared with nonpregnant women, but little is known about the dynamic shifts in oral microbiota during the pregnancy course. Methods : In this study, changes in salivary microbiota in 81 healthy pregnant women throughout the early stage (G1: 9-14 weeks), middle stage (G2: 21-28 weeks), and late stage (G3: 31-38 weeks) were investigated with 16S rRNA sequencing techniques. Correlations between salivary microbiota and maternal characteristics, including fasting blood glucose (FBG) levels, were evaluated. Results : Alpha diversity indexes were stable throughout pregnancy, but significant changes were found in beta diversity measured by weighted and unweighted UniFrac distances. Fourteen dominant trimester-specific taxa were identified using the LEfSe method, including Bacteroidetes in G1, Proteobacteria in G2 and Firmicutes in G3 at the phylum level. Tax4Fun prediction analysis revealed significant changes in Genetic Information Processing, Environmental Information Processing, Unclassified and Human Diseases in G2 and in Metabolism in G3 when compared to G1. Significant correlations were found between FBG levels and microbial composition, and these correlations were independent of gestational diabetes mellitus (GDM) status. Conclusion : Within the limitations of this study, the dynamic changes in salivary microbiota during pregnancy were characterized, and beyond pregnancy, FBG was also involved in shaping the salivary microbiota.