Acute Tolerability and Long-Term Surveillance of Fecal Microbiota Transplantation in Children with Autism: A Real-World Study of 604 Procedures.

INTRODUCTION: Fecal microbiota transplantation (FMT) is a promising adjunctive therapy for autism spectrum disorder (ASD), yet comprehensive, real-world safety data in pediatric populations remain limited. This study aimed to systematically evaluate the safety profile, temporal kinetics, and risk factors for adverse events (AEs) following FMT in children with ASD. METHODS: We conducted a longitudinal observational study of 224 children with ASD (aged 2-17 years) who underwent a total of 604 FMT procedures. Interventions were administered via oral capsules (Caps), nasojejunal tube (NJT), or transendoscopic enteral tube (TET). AEs were systematically graded using common terminology criteria for AEs (CTCAE) criteria, and a multivariate generalized estimating equations (GEE) model was used to identify independent risk factors. RESULTS: In our study, the overall incidence of AEs across 604 procedures was low at 2.5% (15/604 procedures). All documented AEs had an acute onset (< 48 h post-procedure), were strictly Grade 1 (mild) in severity, and spontaneously resolved (median duration 28.0 h). The most frequent symptoms were vomiting and irritability, with no severe or long-term AEs observed. Delivery route significantly impacted safety, and TET exhibited the highest AE rate (26.3%), whereas Caps (1.7%) and NJT (1.8%) demonstrated favorable tolerability. Multivariate analysis identified TET as the independent risk factor for AEs (adjusted odds ratio 21.90, P < 0.001). CONCLUSION: FMT demonstrates favorable acute tolerability in children with ASD, with long-term longitudinal surveillance showing no delayed adverse outcomes. Oral capsules are associated with a low AE rate and represent a preferred delivery route. TRIAL REGISTRATION: Chinese Clinical Trial Registry, ChiCTR2200055943. Registered 28 January 2022, http://www.chictr.org.cn .