This comprehensive review examines how modifications to gut bacteria through probiotics, prebiotics, synbiotics, and fecal transplants can help children with autism. The research found that while all these treatments showed some promise, fecal microbiota transplantation (FMT) produced the most consistent improvements in both autism-related behaviors and digestive symptoms. These microbiota-based approaches work through the gut-brain connection and were generally safe, making them potentially valuable additions to autism management strategies.