Microbiome-gut-brain axis in autism spectrum disorder

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental condition arising from the complex interplay between genetic susceptibility and environmental influences. In recent years, research on the microbiome-gut-brain axis has led to the development of an integrative framework, suggesting that immune, metabolic, endocrine and neuronal signaling pathways may link intestinal homeostasis to the development and function of the central nervous system. The prenatal period represents a critical window of biological vulnerability, during which the maternal microbiome and its associated inflammatory status may shape fetal programming. Although evidence in humans remains largely observational, experimental models support the plausibility of several biological mechanisms, including maternal immune activation, proinflammatory cytokines, microbial metabolites and disruption of the integrity of both the intestinal barrier and the blood-brain barrier. This article synthesizes current evidence regarding the role of the maternal microbiome in ASD, distinguishing epidemiological associations from causal relationships, and discusses the clinical implications for prevention, as well as for the management of gastrointestinal comorbidities.