Maternal Iron Levels and Association With Gestational Diabetes: A Systematic Review and Meta-Analysis.

Background: This systematic review aimed to assess the association of iron level with gestational diabetes mellitus (GDM) risk. Methods: The relevant articles published between January 1, 1995 and January 17, 2023 were identified through a systematic literature search. This study used random effects to summarize the relative risks (RRs) 95% confidence intervals (CIs) of GDM risk and standardized mean differences. This study investigated the association of ferritin exposure with GDM combined with dose-response analysis and explored both linear and nonlinear trends. Results: This meta-analysis selected 30 studies with serum ferritin (SF), 18 studies with serum iron (SI), 4 studies with serum transferrin receptor (sTfR), 5 studies with total iron binding capacity (TIBC), and 4 studies with transferrin (TRF). The summarized RRs comparing persons with the highest concentration categories of SF with the lowest concentration categories of SF with an unadjusted odds ratio were 2.05 (1.67-2.53; I ² = 62.8%, p < 0.001, z = 6.76, p < 0.001) and with an adjusted odds ratio were 1.82 (1.54-2.14; I ² = 12.9%, p=0.312, z = 7.21, p < 0.001). Linear dose-response showed that an increase in SF of 5 μg/L increased the risk of GDM by 2.66% (1.026 [95% CI: 1.017, 1.036], n = 5). The nonlinear dose-response relationship also indicates that the increased SF is consistently associated with an increasing risk of GDM. Conclusion: High ferritin, high iron levels, and low TIBC are associated with an increased risk of GDM.