Fecal Microbiota Transplantation in Children With ASD

This is a single-center, randomized, double-dummy, triple-blind, placebo-controlled, three-arm parallel-group superiority trial. The study aims to compare the efficacy and safety of Fecal Microbiota Transplantation (FMT) administered via two different invasive routes-nasojejunal tube (NJT) and colonoscopy-versus a placebo control in children aged 3-16 years with moderate-to-severe Autism Spectrum Disorder (ASD). A total of 75 participants will be randomized in a 1:1:1 ratio to receive either active FMT via NJT with sham colonoscopy, active FMT via colonoscopy with sham NJT, or placebo via both routes. All participants will continue their stable behavioral interventions throughout the study. The primary outcome is the change from baseline to Week 24 in the total score of the Childhood Autism Rating Scale (CARS). Secondary outcomes include changes in other behavioral and gastrointestinal symptom scores, gut microbiota profiling, and safety assessments over 48 weeks.

Inclusion Criteria: * Aged 3-16 years. * Diagnosed with ASD according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), with a Childhood Autism Rating Scale (CARS) total score ≥36 (moderate-to-severe autism). * Legal guardians fully comprehend the trial's informed consent and voluntarily provide written consent. * Compliance with follow-up visits, examinations, and specimen collection. * No probiotic supplements consumed within the preceding 3 months. Exclusion Criteria: * Use of probiotics or prebiotics within 3 months prior to enrollment. * Antibiotic usage within 1 month prior to enrollment. * Presence of fever (axillary temperature ≥37.5°C). * Dependency on tube feeding. * Severe gastrointestinal conditions requiring immediate intervention (e.g., life-threatening intestinal obstruction, perforation, hemorrhage, ulcerative colitis, Crohn's disease, celiac disease, or eosinophilic esophagitis). * Diagnosis of severe malnutrition, underweight status (BMI-for-age \