The study investigates the microbial colonization of the human gut, focusing on the prenatal and neonatal periods. It collected samples from 15 mother-infant pairs, including maternal feces, placenta, amniotic fluid, colostrum, meconium, and infant feces, to explore microbial transfer and colonization. The results show that the placenta and amniotic fluid harbor distinct microbial communities characterized by low richness and diversity, with Proteobacteria being the predominant phylum. These communities differ significantly from those in maternal feces and infant meconium, suggesting that microbial transfer occurs at the foeto-maternal interface. By 3-4 days after birth, the infant gut microbiota begins to resemble that found in colostrum. The study proposes that the initial steps of gut colonization may be initiated prenatally by distinct microbial communities in the placenta and amniotic fluid, with breast milk continuing to influence the gut microbiota postnatally. The findings highlight the importance of early microbial interactions in programming immune and metabolic pathways, which can impact health and disease later in life.The study investigates the microbial colonization of the human gut, focusing on the prenatal and neonatal periods. It collected samples from 15 mother-infant pairs, including maternal feces, placenta, amniotic fluid, colostrum, meconium, and infant feces, to explore microbial transfer and colonization. The results show that the placenta and amniotic fluid harbor distinct microbial communities characterized by low richness and diversity, with Proteobacteria being the predominant phylum. These communities differ significantly from those in maternal feces and infant meconium, suggesting that microbial transfer occurs at the foeto-maternal interface. By 3-4 days after birth, the infant gut microbiota begins to resemble that found in colostrum. The study proposes that the initial steps of gut colonization may be initiated prenatally by distinct microbial communities in the placenta and amniotic fluid, with breast milk continuing to influence the gut microbiota postnatally. The findings highlight the importance of early microbial interactions in programming immune and metabolic pathways, which can impact health and disease later in life.