The impact of maternal vitamin D levels during pregnancy and risk of autism spectrum disorder and attention deficit hyperactivity disorder diagnosis and symptoms in offspring: a systematic review and dose-response meta-analysis.

INTRODUCTION

Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD) have a complex etiology involving both genetic and environmental factors, with mechanisms still unclear. In this review, we investigated the association between maternal 25-hydroxyvitamin D status during pregnancy and the risk of diagnosis and symptoms of ASD and ADHD in offspring in developmental age.

METHODS

We searched online databases up to February 13, 2026. We conducted a quantitative meta-analysis by comparing the exposure categories and using a dose-response approach across the entire exposure range.

RESULTS

We included 15 eligible studies: 8 related to ASD and ASD symptoms, 5 related to ADHD and ADHD symptoms, and 2 to both. Comparing high versus low maternal vitamin D status, we found an inverse association with both lower ASD risk (RR = 0.91; 95% CI 0.87-0.96) and ADHD risk (RR = 0.90; 95% CI 0.82-0.99). In the dose-response pooled analysis, ASD risk linearly decreased by 9% for every 10 nmol/L increase in maternal serum vitamin D levels. Higher vitamin D levels were also inversely associated with ADHD symptoms, though estimates were statistically imprecise due to the limited number of studies.

CONCLUSIONS

Higher vitamin D status during pregnancy appears to be linearly associated with a reduced risk of ASD and ADHD diagnoses and symptoms in offspring, with no evidence of thresholds across the investigated exposure range. These findings suggest the opportunity to assess vitamin D levels during pregnancy, and to consider its supplementation in deficiency cases, to support fetal brain development and promote neuroprotection.