(1) Background: The colonization characteristics of infant gut microbiota are influenced by many factors at various stages, but few studies have explored the longitudinal effects of environmental tobacco exposure and quantitative weaning time on young children’ intestinal flora. The purpose of this study was to characterize the evolution of intestinal microflora in young children aged 0-2 years and the longitudinal effects of environmental tobacco exposure and weaning time on young children aged 6, 12, and 24 months.
(2) Methods: A total of 37 maternal and children pairs were included in a tertiary general hospital in China and followed up for 2 years. General demographic information was collected on mothers (after delivery, 6 months, 12 months) and young children (6 months, 12 months, 24 months), including frequency of exposure and time of weaning, through self-made questionnaires. Fecal samples were collected from mothers in the third trimester of pregnancy and infants at 6, 12 and 24 months, and analyze the microbiota results using the V3-V4 gene sequence of 16S rRNA.
(3) Results: the diversity of intestinal microflora in young children was the highest at 24 months and most similar to that in mothers. Weaning time was positively correlated with Lactobacillus in the intestines of infants aged 0 to 12 months. The diversity of microbiota exposed to environmental tobacco smoke at 6 months was lower than that of the non-exposed group, and the higher the exposure at 6-12 months, the lower the abundance of Blautia.
(4) Conclusion: The gut microbiota of young children becomes more mature and complicated with age. The extension of complete weaning time to about 12 months is conducive to the colonization of beneficial bacteria. And the long-term exposure of children and the environment of tobacco smoke will affect the dysbiosis of gut microbiota.