Preterm birth, which occurs before the entire gestation is completed, causes serious health challenges for newborns. The gastrointestinal tract often shows delayed development and poor function in nutrient utilization and immune response. Preterm neonates are faced with difficulties in growth, are more vulnerable to infections, and have a higher risk of developing inflammatory diseases. One key factor in these outcomes is the abnormal development of intestinal microbiota. In premature neonates, gut microbes tend to show lower diversity and changes in several bacteria. The gut dysbiosis can disrupt gut function and contribute to complications like necrotizing enterocolitis, sepsis, and even long-term metabolic and neurodevelopmental disorders. This review brings together current research on how premature birth affects the growth, gut development, and overall health of infants, with a focus on changes in microbial colonization. In addition, we discuss how gut microbiota plays a role in shaping the immune system and influencing brain development. There is growing interest in using breast milk, specialized nutrition, and probiotics to improve microbial balance in premature infants. Preterm birth alters intestinal development and microbial colonization, making infants vulnerable to gut dysbiosis and disease. These changes contribute to a heightened risk of neonatal diseases such as NEC, sepsis, and long-term neurodevelopmental and metabolic disorders. Evidence highlights the critical role of commensal microbes and their metabolites in promoting epithelial maturation, immune balance, and gut-brain signaling. Advancing neonatal care will require precision approaches based on microbial profiling, targeted nutritional strategies, and a deeper understanding of host-microbe interactions to improve health in preterm infants. Therefore, this review focuses on integrating recent evidence of microbial development and preterm infant health, highlighting the gut-brain axis in relation to metabolic disorders, and emphasizing how gut dysbiosis links clinical outcomes with mechanistic insights in neonatal care.
