Serum vitamin D levels and COVID-19 during pregnancy: A systematic review and meta-analysis

Background: Serum vitamin D levels are reported to be associated with the risk of incidence and severity of COVID-19 in the general population. During pregnancy, immune system alterations in line with changes in vitamin D metabolism may affect the course of COVID-19. Thus, we aimed to systematically review the association between vitamin D, pregnancy, and COVID-19.Methods: A systematic literature search was conducted in PubMed, Scopus, Web of Science, Embase, and Google Scholar until the end of May 2022. Mean differences (MD) with 95% CI were used as desired effect sizes to assess the association of serum vitamin D levels with the risk of incidence and severity of COVID19 in pregnant women.Results: Among 259 records, 7 and 6 studies were included in the systematic review and meta-analysis, respectively. All included studies had acceptable quality. Our results demonstrated an insignificant difference between infected women and non-infected controls (MD = -2.55 ng/ml, 95% CI: -6.85 - 1.74). But serum vitamin D levels in severe/moderate cases compared to mild ones (MD = -2.71 ng/ml, 95% CI: -4.18 to -1.24) are significantly lower. Conclusion: Based on the current evidence, serum vitamin D level does not associate with the risk of SARS-CoV-2 infection among pregnant women, but we find a significant association with the severity of the disease. These findings may be helpful in similar conditions and future studies to better understand the complex immune alterations during pregnancy.(c) 2022 European Society for Clinical Nutrition and Metabolism. Published by Elsevier Ltd. All rights reserved.