Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 54 11 2025 11 28 2356 2366 Keli Qu Department of Child Healthcare, Shandong Provincial Third Hospital, Shandong University, Jinan, China Zhiliang Gao Department of Pediatric, Binzhou Hospital of Traditional Chinese Medicine, Binzhou, China Cong Chang Department of Rehabilitation, Binzhou Municipal Hospital, Binzhou, China Meizhe Gao Department of Child Healthcare, Shandong Provincial Third Hospital, Shandong University, Jinan, China 2025 03 12 2025 08 09 Background: We examined and compared microbiological variables, trace elements, and biological markers in autistic children. Methods: Several databases, including the Cochrane Library, PubMed, OVID, Google Scholar, and Embase, were utilized for data collection and analysis. We studied meta-analysis data and used a continuous model with fixed or random effects to get mean differences (MD) with 95% confidence intervals (CIs). Twenty-seven studies involving 2557 children from 2014 to 2024 were analyzed. Results: Autism spectrum disorder had significantly higher C-reactive protein (MD, 1.25; 95% CI, 0.11-2.39, P=0.03), interleukin 6 (MD: 2.80; 95%CI, 1.13-4.46, P=0.001), serotonin (MD, 111.92; 95%CI, 63.75-160.09, P<0.001), Faecalibacterium (MD, 0.48; 95%CI: 0.29-0.66, P<0.001), and Parabacteroides (MD, 0.20; 95%CI: 0.14-0.26, P<0.001), lower oxytocin (MD, -53.24; 95% CI, -73.39- -33.09, P<0.001), and serum iron (MD, -5.78; 95% CI, -9.43- -2.13, P=0.002) compared to control in children. Conclusion: Autism spectrum disorder had significantly higher C-reactive protein, interleukin-6, serotonin, Faecalibacterium, Parabacteroides, lower oxytocin, and serum iron compared to control in children. Further research studies with larger sample sizes are needed. https://ijph.tums.ac.ir/index.php/ijph/article/view/38484 https://ijph.tums.ac.ir/index.php/ijph/article/download/38484/8695