MATERNAL MICROBIOTA TRANSMISSION AND ITS ROLE IN THE FORMATION OF THE INFANT IMMUNE SYSTEM (LITERATURE REVIEW)

The acquisition of the human microbiota begins at birth and is closely intertwined with the early development and functional programming of the immune system. Growing evidence demonstrates that initial microbial colonization is essential for establishing immune tolerance, promoting the maturation of epithelial and mucosal barriers, and coordinating host defense mechanisms during infancy. Large-scale metagenomic studies have revealed maternal transmission of specific microbial taxa, particularly strains of Bifidobacterium and Bacteroides, which can persist in the infant gut for extended periods. These early colonizers play a crucial role in the degradation of human milk oligosaccharides, the biosynthesis of short-chain fatty acids (SCFAs), and the modulation of immune signaling pathways. Disruption of maternal microbial transmission—most often associated with cesarean delivery or perinatal antibiotic exposure—has been linked to reduced microbial diversity, delayed colonization by beneficial commensals, increased abundance of opportunistic pathogens, and a higher risk of immune-mediated disorders, including allergic and autoimmune diseases. This review highlights the principal bacterial species transmitted from mother to infant, the main routes of transmission (skin contact and breastfeeding), and their potential contributions to early immune development. Vertical transmission of maternal microbiota provides a foundational microbial inoculum that supports immunological education, metabolic homeostasis, and protection against pathogens. In light of current obstetric practices, including the rising prevalence of cesarean delivery and routine use of antibiotics, preserving and promoting maternal–infant microbial transfer should be regarded as a critical target for interventions in neonatal and preventive healthcare.