Introduction Maternal weight status and gestational weight gain (GWG) critically affect maternal and neonatal health. The infant gut microbiome is a key predictor of short- and long-term child health. Therefore, investigating how maternal weight characteristics influence the composition and establishment of the infant’s gut microbiome is essential. Objective To evaluate the impact of excessive GWG on the infant gut microbiome. Methodology PubMed and Scopus were systematically searched for studies on GWG from September 1 st until October 1 st , 2025. Data on infant gut microbiome characteristics and their relation to maternal weight change during pregnancy were extracted. The systematic review is registered in PROSPERO (CRD 420251181399). Results A total of 15 studies met the inclusion criteria and were included in this review. Excessive Gestational Weight Gain (EGWG) consistently appeared to impair infant gut microbial alpha diversity, an effect that persisted up to 12 months. Taxonomically, EGWG caused a shift away from beneficial Bacteroides toward opportunistic/pathogenic genera (e.g., C. difficile ). The negative effects are synergistically exacerbated by co-occurring Gestational Diabetes Mellitus (GDM) and are functionally characterized by an independent shift toward microbial carbohydrate degradation and vitamin synthesis pathways. Clinically, this EGWG-induced dysbiosis is linked to increased early childhood weight gain. Conclusion EGWG is an independent, critical determinant of persistent infant gut dysbiosis, characterized by taxonomic and functional shifts. These findings establish EGWG as a key modifiable maternal factor, linking gestational health to infant gut microbiome and health. Systematic Review Registration https://www.crd.york.ac.uk/PROSPERO/view/CRD420251181399 , identifier: CRD 420251181399.
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