Evidence of the functions of vitamin D in pregnant women in COVID-19: a systematic review

Introduction: In the world, about 1 million people suffer from vitamin D deficiency. Vitamin D deficiency in pregnant women increases maternal mortality and morbidity rates. In the scenario of COVID-19, it is known that the immune response, inflammation, and coagulation are modulated by vitamin D activity. Objective: It was to analyze the main considerations of the effects of vitamin D on pregnant women and fetuses in the scenario of COVID-19, presenting the mechanisms of inflammatory and immunological processes in an attempt to mitigate the worsening of comorbidities and deaths. Methods: The systematic review rules of the PRISMA Platform were followed. The research was carried out from September to October 2022 in Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 210 articles were found, 82 articles were evaluated and 32 were included in this systematic review. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 28 studies with a high risk of bias and 28 studies that did not meet GRADE. Most studies showed homogeneity in their results, with I2 =98.9% >50%. There is a relationship between vitamin D status and the severity of COVID-19 in pregnant women. Vitamin D levels are low in pregnant women with COVID-19. Furthermore, there is a significant difference regarding the level of vitamin D and the severity of COVID-19 in pregnant women. Maintaining adequate vitamin D levels may be useful as an approach to preventing an aggressive course of inflammation induced by this novel coronavirus in pregnant women.