Vitamin D deficiency and anemia in pregnant women: a systematic review and meta-analysis

Context Epidemiological studies suggest an association between vitamin D deficiency and anemia. Evidence of this relationship in pregnant women, however, is scarce. Objective The aim of this systematic review was to investigate the association between vitamin D deficiency and gestational anemia through observational studies. Data Sources The PubMed, Scopus, Web of Science, ScienceDirect, Embase, and Virtual Health Library databases were searched from inception to April 2021. Study Selection Original articles reporting observational studies that investigated the association between vitamin D deficiency and gestational anemia were included. Articles that did not have an abstract, as well as reviews articles, experimental studies, and editorials, were excluded. Two reviewers independently performed study selection, data extraction, and assessment of study quality. Disagreements between the reviewers were resolved by a third reviewer. Data Extraction Study quality was assessed by 2 scales. Data were extracted from eligible studies and arranged in a 2 x 2 table. Odds ratios with 95% confidence intervals for the risk of the outcome were estimated using a fixed-effect model. Results In total, 985 studies were retrieved, of which 17 were included in the systematic review: 11 cohort studies, 3 case-control studies, and 3 cross-sectional studies. For the meta-analysis, 8 studies with a total of 6530 women were included. There was a 61% increase in the odds of anemia in pregnant women with vitamin D deficiency (OR = 1.61; 95%CI, 1.41-1.83; I-2 = 48%). Conclusions Vitamin D deficiency may be a risk factor for anemia in pregnant women. Systematic Review Registration PROSPERO registration no. CRD42020182697.