Compelling evidence supports a link between early-life gut microbiota and the metabolic outcomes in later life. Using an early-life antibiotic exposure model in BALB/c mice, we investigated the life-course impact of prenatal and/or postnatal antibiotic exposures on the gut microbiome of offspring and the development of metabolic dysfunction-associated steatotic liver disease (MASLD). Compared to prenatal antibiotic exposure alone, postnatal antibiotic exposure more profoundly affected gut microbiota development and succession, which led to aggravated endotoxemia and metabolic dysfunctions. This was primarily resulted from the overblooming of gut