Autism Spectrum Disorder (ASD) is a neurodevelopmental condition that affects communication, behavior, sensory processing, and daily functioning. Recent research suggests that the gut microbiome, the community of microorganisms living in the gastrointestinal tract, may influence brain development and function through the gut-brain and gut-motor axes. Alterations in gut microbiome characteristics have been reported in children with ASD and may be associated with differences in neurodevelopmental outcomes.

This observational study aims to investigate the association between gut microbiome characteristics and neurodevelopmental functioning in children with ASD. The study will evaluate multiple domains of functioning, including motor performance, sensory processing, behavior, cognition, sleep, and participation in daily activities. Gut microbiome characteristics will be assessed using stool sample analysis, and neurodevelopmental outcomes will be measured using standardized assessments and validated questionnaires.

The findings of this study may improve understanding of the relationship between the gut microbiome and neurodevelopmental functioning in children with ASD and provide insights into the role of the gut-motor axis in shaping functional outcomes. This knowledge may support future research and contribute to the development of more personalized approaches to assessment and rehabilitation in ASD.

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterized by impairments in social communication, restricted and repetitive behaviors, sensory processing differences, and variable functional abilities across developmental domains. Increasing evidence suggests that the gut microbiome may play a role in neurodevelopment through bidirectional communication pathways linking the gastrointestinal system and the central nervous system. These interactions, commonly described as the gut-brain axis, have been implicated in behavioral, cognitive, sensory, and motor processes. More recently, the concept of the gut-motor axis has emerged, highlighting potential relationships between gut microbial composition and motor functioning.

Several studies have reported alterations in gut microbiome composition among children with ASD compared with typically developing peers. However, existing research has largely focused on autism symptom severity, behavioral manifestations, or gastrointestinal symptoms, while the association between gut microbiome characteristics and broader neurodevelopmental functioning remains insufficiently explored. Furthermore, few studies have examined multiple functional domains simultaneously within a rehabilitation framework.

The present study aims to investigate the association between gut microbiome characteristics and neurodevelopmental functioning in children with ASD. A multidomain assessment approach will be employed to evaluate neurodevelopmental outcomes encompassing motor performance, sensory processing, behavioral function, cognitive functioning, sleep, and participation in daily activities. Gut microbiome characteristics will be assessed through stool sample analysis using established microbiological methods. Neurodevelopmental outcomes will be evaluated using standardized assessments and validated caregiver-reported instruments.

By examining the relationship between gut microbiome characteristics and multidimensional functional outcomes, this study seeks to enhance understanding of the gut-motor axis in ASD and identify potential microbiome-related factors associated with neurodevelopmental functioning. The findings may contribute to the growing body of evidence on microbiome-neurodevelopment interactions and inform future translational and rehabilitation research in children with ASD.

Inclusion Criteria:

• Children aged 3 to 12 years
• Clinical diagnosis of Autism Spectrum Disorder (ASD) according to DSM-5/ICD criteria and confirmed from medical records or specialist assessment
• Stable clinical status at the time of enrollment
• Parent/legal guardian willing to provide written informed consent
• Child able to undergo stool sample collection and neurodevelopmental assessments
• Parent/caregiver able to complete questionnaires and provide dietary and medical history

Exclusion Criteria:

• Use of systemic antibiotics, probiotics, prebiotics, synbiotics, or bowel-cleansing agents within the previous 4-12 weeks before stool collection
• Presence of acute gastrointestinal infection or acute febrile illness at the time of assessment
• Known chronic gastrointestinal disorders that may independently alter the gut microbiome, such as inflammatory bowel disease, celiac disease, short bowel syndrome, or chronic intestinal malabsorption
• Major neurological, genetic, or metabolic disorders other than ASD that may independently affect neurodevelopment
• Current use of medications known to significantly affect gut microbiota or bowel motility, if clinically relevant to your protocol
• Inability to provide stool sample or complete the required assessments
• Refusal of consent by parent/legal guardian

The study population will consist of children aged 3 to 12 years with a confirmed diagnosis of Autism Spectrum Disorder (ASD) who are receiving care at participating pediatric rehabilitation, developmental, neurology, psychiatry, and autism care centers. Eligible participants will undergo stool sample collection for gut microbiome analysis and multidomain neurodevelopmental assessment, including evaluation of autism severity, gross motor function, sensory processing, cognitive functioning, behavioral function, sleep, participation, quality of life, gastrointestinal symptoms, dietary intake, and anthropometric nutritional status. Written informed consent will be obtained from parents or legal guardians prior to participation.

Individual participant data (IPD) may be shared upon reasonable request following publication of the study findings, subject to institutional policies, ethical approval requirements, participant confidentiality protections, and applicable data-sharing agreements. A final decision regarding IPD sharing will be made after completion of the study and in accordance with institutional and regulatory guidelines.