Objective: To evaluate the relationship between serum vitamin D levels and autism spectrum disorders (ASD) in children by Meta-analysis. Methods: Medline

EMBase

PubMed

Scopus

the Cochrane Library

EBSCO

Web of Science

CBMdisc

CNKI

Wanfang database and VIP database were retrieved to collect case-control studies related to vitamin D levels and ASD in children by Meta-analysis. Weighted mean difference (WMD) and 95% CI were used as the combined effect size

and Meta-analysis was performed by using Rev Man 5.3 and Stata 16.0 software. Publication bias assessment and sensitivity analysis were performed. Results: A total of 14 literature were collected

including 2

403 participants (1

135 children with ASD and 1

268 healthy controls). Meta-Analysis showed that serum 25-hydroxyvitamin D (25-(OH)D) level in children with ASD was significantly lower than that in the control group (WMD=-8.91

95%CI: from -12.45 to -5.37

P<0.01). The results of subgroup analysis showed that the serum 25-(OH)D level in children with ASD from China was significantly lower than that in the control group (WMD=-10.81

95%CI: from -16.80 to -4.82

P<0.01)

the serum 25-(OH)D level in children with ASD from the Middle East was significantly lower than that in the control group (WMD=-9.35

95%CI: from -18.09 to -0.60

P=0.04). In European and American countries (except for the Middle East countries)

there was no significant difference in serum 25-(OH)D level between children with ASD and the control group (WMD=-6.22

95%CI: from -12.87 to 0.44

P=0.07). Conclusion: Vitamin D deficiency may be a risk factor for ASD in children.