A Review of Gut Microbiota Dynamics: From Healthy Gestation to Gestational Diabetes in Human and Mouse Models

Over the past decades, gut microbiota has emerged as a critical modulator of human health and disease. Pregnancy involves substantial microbiota remodelling that influences offspring development, yet mechanisms linking maternal microbiota changes to gestational diabetes mellitus (GDM) remain unclear. The current literature lacks a comprehensive synthesis of pregnancy microbiota dynamics across healthy gestation to GDM, comparative human-murine analysis, and pregnancy-specific mechanistic frameworks distinct from type 2 diabetes models. This narrative review comprehensively synthesised evidence on gut microbiota composition in healthy pregnancy and GDM (2005-2025, NCBI PubMed) to identify convergent signatures and articulate pregnancy-specific mechanisms. Early pregnancy microbiota resembles non-pregnant individuals, whereas late pregnancy exhibits increased lactic acid-producing bacteria and reduced Firmicutes-to-Bacteroidetes (F/B) ratios. GDM exhibits pathological dysbiosis with elevated F/B ratios and reduced Bifidobacterium. Critically, GDM butyrate-producer patterns diverge from type 2 diabetes, suggesting pregnancy-specific mechanisms beyond glucose homeostasis. Despite these insights, methodological heterogeneity and cross-sectional designs constrain definitive conclusions. Longitudinal studies with standardised sequencing are essential to confirm consistent signatures and enable rational design of microbiota-modulating interventions (prebiotics, probiotics, synbiotics, postbiotics, diet) to optimise maternal health, prevent GDM, and support offspring development.