Establishment of the early gut microbiota in vaginally delivered infants: the influence of maternal gut microbiota outweighs vaginal microbiota.

UNLABELLED

Gut microbiota is one of the largest microbial communities within the human body, yet its origins and early developmental processes remain not fully understood. This study collected samples from 26 mother-infant pairs from the third trimester to 14 days postpartum, using 16S rDNA sequencing and Source Tracker analysis to investigate the dynamic changes and sources of early infant gut microbiota. Results showed that maternal gut microbiota at 32 weeks of gestation was the primary source of meconium microbiota in vaginally delivered infants and continued to influence day-14 gut microbiota, while maternal vaginal microbiota contributed minimally (<1%). Regardless of bacterial presence in breast milk, maternal gut microbiota remained a critical source for day-14 gut microbiota of vaginally delivered infants. Placental microbiota was also an important source of meconium microbiota across different delivery modes. In cesarean-delivered infants, the origins of gut microbiota were more complex, with a higher proportion of "transient bacteria" in meconium, potentially impacting the stable colonization of gut microbiota. However, by day 14, the gut microbiota of cesarean and vaginally delivered infants became similar post-breastfeeding. Correlation network analysis revealed intricate maternal-infant microbial interactions, indicating that maternal microbes may influence the colonization of infant gut microbiota. Shared taxa analysis showed that functional flora might exist in the placenta. Meanwhile, beneficial anaerobes like significantly increased in infant day-14 gut microbiota, suggesting their potential role in gut health. Overall, this study provides novel insights into the colonization and developmental patterns of early infant gut microbiota.

IMPORTANCE

Gut microbiota exerts a significant impact on an individual's long-term health; however, its origins and colonization processes remain to be fully elucidated. This study revealed that early infant gut microbiota of vaginally delivered infants primarily derived from maternal gut microbiota, which began colonizing the fetus as early as 32 weeks of gestation. In contrast, the contribution of maternal vaginal microbiota to early infant gut microbiota was quite limited. Moreover, placental microbiota also constituted an important source for the fetal gut microbiota. These findings provide novel insights into the developmental mechanisms of infant gut microbiota and highlight the important role of maternal microbes in the early colonization of infant gut microbiota.