BackgroundWe aimed to provide a comprehensive understanding of the associations between iron metabolism and gestational diabetes mellitus (GDM) by examining multiple iron-related indicators. MethodsWe conducted a prospective study involving 907 Chinese pregnant women. Enzyme-linked immunosorbent assay (ELISA) was used to measure serum concentrations of iron-related indicators during the first trimester (≤ 14 weeks of gestation). GDM outcomes were measured through oral glucose tolerance tests (OGTT) conducted between weeks 24 and 28 of gestation. ResultsSubjects with iron-related indicators below the 10th percentile (except for serum iron and soluble transferrin receptor) had a higher risk of GDM compared to normal subjects (10th-90th percentiles). The ORs (95%CI; p-value) were 1.88 (1.10, 3.20; P=0.020) for ferritin, 1.88 (1.10, 3.19; P=0.020) for hepcidin. Higher levels of ferritin (> 90th percentile) were associated with a higher risk of abnormal fasting blood glucose, while lower levels (< 10th percentile) of ferritin, hepcidin, and transferrin were associated with a higher risk of one-hour postprandial glucose ≥ 8.6mmol/L in the OGTT. ConclusionsLower levels (< 10th percentiles) of several iron-related indicators (ferritin, hepcidin, and transferrin) were associated with a higher risk of GDM and abnormal blood glucose compared to normal subjects.