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Antibiotic-induced dysbiosis has been increasingly implicated in a range of pediatric outcomes, yet the concept remains variably defined and often inconsistently applied. The purpose of this review is to provide an overview and critical evaluation of the available data regarding the effects of early-life exposure to β-lactam antibiotics on the developing microbiome. We conducted a narrative review of experimental and epidemiological studies examining β-lactam exposure during pregnancy, the perinatal period, and early childhood was conducted. β-lactams induce reproducible alterations in microbial composition, diversity, and metabolic function, including decreases in Bifidobacterium and Lactobacillus and a relative increase in Enterobacteriaceae and other facultative anaerobes, especially in early life. Reduced microbial diversity and changed short-chain fatty acid-producing taxa often accompany these compositional changes. However, associations with immune, metabolic, and neurodevelopmental outcomes are heterogeneous and frequently confounded by indication host-related factors. Evidence for causality in humans remains limited despite strong mechanistic support from animal models. Current data support cautious interpretation, even though β-lactam-associated microbiome perturbations may contribute to disease susceptibility during vulnerable developmental windows. While mechanistic and longitudinal evidence continues to develop, antibiotic stewardship focused on appropriate indication and duration is still crucial.