Higher iron status during pregnancy may increase gestational diabetes mellitus (GDM) risk via iron-induced oxidative stress, leading to insulin resistance and impairing pancreatic β-cell function through lipid peroxidation and/or DNA damage. However, associations between maternal iron status and GDM remain controversial. Hemoglobin is a clinically routine iron status indicator measured across pregnancy. This study aims to explore whether hemoglobin levels (and changes) in early and mid-pregnancy are associated with GDM risk. This study employed longitudinal data from a prospective cohort study conducted from December 2018 to September 2021. Pregnancy women at early pregnancy were recruited in the birth cohort, and 6420 eligible women were included in the final analysis of the present study. Data collected at early and mid-pregnancy was used. Generalized linear models were applied to evaluated the associations between hemoglobin and GDM. 49.6% (3184 of 6420) and 7.1% (458 of 6420) of women had high hemoglobin in early and mid-pregnancy, respectively. 92.6% (5946 of 6420) of women had decreased hemoglobin concentrations from early to mid-pregnancy. The overall incidence of GDM was 23.1% (1484 of 6420). Higher hemoglobin concentrations (for every 10 g/L increase) were associated with increased risk of GDM (early pregnancy: RR: 1.09, 95%CI: 1.04, 1.14; mid-pregnancy: RR: 1.07, 95%CI: 1.01, 1.13). High hemoglobin in early or/and mid-pregnancy significantly increased GDM risk (early pregnancy: RR: 1.11, 95%CI: 1.01, 1.21; mid-pregnancy: RR: 1.19, 95%CI: 1.03, 1.39; both periods: RR: 1.36, 95%CI: 1.15, 1.61). Significantly reduced risk of GDM was observed with every 10 g/L decrease in hemoglobin from early to mid-pregnancy (RR: 0.87, 95%CI: 0.81, 0.93), especially in women with the High-Decrease change pattern (RR: 0.87, 95%CI: 0.80, 0.95). Maternal high hemoglobin levels in early and/or mid-pregnancy are associated with increased GDM risk, and a decline in hemoglobin levels from early to mid-pregnancy is associated with reduced GDM risk. Not applicable.
Liu et al. (Thu,) studied this question.