Association between the ferritin level and risk of gestational diabetes mellitus: A meta‐analysis of observational studies

AIMS/INTRODUCTION: The relationship between ferritin and the risk of gestational diabetes mellitus (GDM) has not been established. Thus, we carried out a meta‐analysis based on the current literature. MATERIALS AND METHODS: We searched relevant databases on Embase, PubMed, Cochrane Library and Web of Science before 10 May 2019 to determine the relationship between ferritin and the risk of GDM. The relative risks and 95% confidence intervals of GDM risk were summarized using a random effects model. Studies using categories of ferritin as exposure were combined by dose–response analysis. We carried out both linear and non‐linear trends. We also carried out subgroup analysis, whether or not the studies adjusted for potential confounders, and meta‐regression analysis to explore the source of heterogeneity. Sensitivity analysis was carried out to explore the robustness of the meta‐analysis results. RESULTS: A total of 10 studies involving 4,690 participants were identified. The summary relative risk comparing persons with the highest concentration categories of ferritin with the lowest concentration categories of ferritin was 1.87 (95% confidence interval 1.50–2.34; I (2) = 20.1%). Linear dose–response showed that an increase in ferritin of 10 μg/L increased the risk of GDM by 8% (1.08, 95% confidence interval 1.05–1.13, I(2) = 55.1%; n = 4). A non‐linear dose–response relationship also showed a consistently increasing risk of GDM with increased ferritin. No evidence of publication bias was detected. CONCLUSIONS: The findings from this meta‐analysis suggest that increased ferritin levels are associated with an increased risk of GDM; however, we require further prospective cohort studies to confirm the results, especially the dose–response relationship between ferritin and GDM.