Iron-Related Factors in Early Pregnancy and Subsequent Risk of Gestational Diabetes Mellitus: the Ma'anshan Birth Cohort (MABC) Study.

Iron is an essential micronutrient while its excessive load has been related to the etiology of diabetes. We used data of 3289 pregnant women from the Ma'anshan birth cohort (MABC) study in China to examine the associations of three iron-related factors (i.e., serum iron (SI) concentration, hemoglobin level, and use of iron supplements) with risk of gestational diabetes mellitus (GDM). Emphatically explore the potential non-linear relationship between SI concentration and risk of GDM. SI concentration was measured in fasting blood using inductively coupled plasma mass spectrometry (ICP-MS). GDM diagnosis was determined by 75 g oral glucose tolerance test at 24~28 weeks. Restricted cubic splines with three knots were used to examine potential non-linear relationship between SI concentration and GDM risk. We observed a U-shape relation between SI concentration in the first trimester and risk of GDM. In the multivariate-adjusted model, compared with the middle level (ln(SI), 7.1-7.7 μg/L), both the lowest level (ln(SI) ≤ 7.1 μg/L) (odds ratio (OR) = 1.35, 95% confidence interval (CI) = 1.04-1.76) and the highest level (ln(SI) > 7.7 μg/L) (OR = 1.63, 95%CI = 1.16-2.28) increased risk of GDM. Associations of hemoglobin level in the first trimester and risk of GDM attenuated to non-significance after adjustment for pre-pregnancy body mass index (BMI) and blood pressure. Pre-pregnancy iron supplement use was associated with an increased risk of GDM (OR = 1.57, 95%CI = 1.06-2.32). In conclusion, the three iron-related factors are all related to GDM risk on some level.