Early-life gut microbiome development and its potential long-term impact on health outcomes.

The initial gut colonization of the infant plays a pivotal role in shaping the immune system, developing the intestinal tract, and influencing host metabolism, all of which are strongly influenced by several determinants, such as gestational age at birth, mode of delivery, neonatal feeding practices, early-life stress (ELS), and exposure to perinatal antibiotics. However, resulting gut microbiome (GM) dysbiosis may alter this developmental programming, leading to long-term adverse health outcomes. This narrative review synthesizes current knowledge on early-life GM development and its long-term impact on health. Specifically, it addresses how early-life GM dysbiosis may affect the trajectory of physiological processes, predisposing individuals to conditions such as allergic diseases, metabolic disorders, type 1 diabetes, inflammatory bowel disorders, and atherosclerotic cardiovascular diseases. In addition, it examines the influence of probiotic and prebiotic supplementation during pregnancy and early life in shaping infant GM composition, as well as the impact of ELS-induced GM dysbiosis on mental health. Recent research suggests that the early-life microbiota initiates long-lasting effects, and inadequate or insufficient microbial exposure triggers inflammatory responses associated with several physiological conditions. Although several studies have reported a connection between ELS and the GM during both prenatal and postnatal periods, a unified microbiome signature linked to either prenatal or postnatal stress remains to be fully elucidated. Thus, future studies are needed to establish causality and determine whether modifiable factors affecting the GM could be targeted to improve gut health, especially in children exposed to contextual stress or adverse conditions.