Vitamin D levels and its influencing factors in pregnant women in mainland China: A systematic review and meta-analysis

Maternal vitamin D deficiency is a prevalent public health issue worldwide. While isolated reports from certain cities in China have highlighted the existence of maternal vitamin D deficiency, no nationwide investigation has been conducted on this topic. Therefore, we conducted a meta-analysis and systematic review to examine the prevalence and associated influencing factors of maternal vitamin D deficiency in mainland China. This study aims to provide a theoretical foundation for future prevention and supplementation strategies for maternal vitamin D. We retrieved relevant Chinese and English literature on the status of maternal vitamin D deficiency in mainland China from databases such as CNKI, Wanfang Data, VIP, CBM, Web of Science, Google Scholar, and PubMed. The literature search and database construction were conducted until September 8, 2023. Data were extracted and synthesized following PRISMA guidelines.After literature screening and quality assessment, we performed meta-analysis, sensitivity analysis, and identified publication bias using RevMan 5.3 software. A total of 26 articles were reviewed, involving 128,820 pregnant women. Among them, 108,768 had vitamin D insufficiency or deficiency, resulting in a prevalence of 84% (95% CI: 81%~88%). Subgroup analysis revealed the highest prevalence of vitamin D deficiency or insufficiency among pregnant women in mainland China to be in the northwest region (94%, 95% CI: 94%~95%). Furthermore, the highest prevalence was observed during the winter and spring seasons (80%, 95% CI: 77%~83%) and in the early stages of pregnancy (93%, 95% CI: 90%~95%). Significant statistical differences (P