The establishment of the human microbiota begins gradually from birth and undergoes significant changes during the first 1000 days of life (Xiao and Zhao, 2023). This critical period provides windows of "opportunity" for the acquisition of the microbiota and education of the immune system, which ultimately condition well-being and long-term health. The maternal microbiota plays an influential role in shaping these acquisitions (Tian et al., 2023). Therefore, it is natural to say that good maternal health directly contributes to the health of both the fetus and the newborn. However, numerous factors can influence these processes (genetic factors, age, general health, lifestyle, medications, mode of delivery, diet, environmental factors). The complexity of the microbiota often makes it challenging to establish direct links between dysbiosis or disruptions in the mother -child and child -environment dialogues and the appearance of various pathologies. Optimal development of the newborn's gut microbiota can be achieved through a full -term birth, vaginal delivery and breastfeeding which are considered the golden rules. In this regard we will present recent research findings that aim to enhance our understanding of the establishment and dynamics of the gut microbiota in newborns, particularly in relation to immune system education. Disturbances of theses interactions within the context of different pathologies will also be highlighted. (c) 2024 The Author(s). Published by Elsevier Masson SAS on behalf of Soci & eacute;t & eacute; fran & ccedil;aise de nutrition.