Gut microbiome and pregnancy complications: emerging evidence and mechanistic insights

The gut microbiome undergoes significant alterations during pregnancy. Perturbations in these microbial communities are increasingly associated with a range of pregnancy complications, including miscarriage, gestational diabetes mellitus, preeclampsia, preterm birth, and fetal growth restriction, among others. This review synthesizes current evidence on the dynamic changes in the maternal gut microecosystem including bacterial, fungal, and viral communities throughout gestation and examines its relationships with various pregnancy complications. We also summarize the underlying mechanisms driving these interactions, focusing on metabolic regulations involving short-chain fatty acids, bile acids, indoles, sex hormones, intestinal barrier integrity, and the modulation of maternal immune responses essential for fetal tolerance. Additionally, we discuss the lasting impact of the maternal microbiome on offspring health via vertical transmission and developmental programming. This review provides a conceptual framework that integrates mechanistic insights with clinical findings, with the goal of informing future research and supporting the development of microbiome-based interventions to improve maternal and neonatal health outcomes.