SF

This retrospective cohort study examined the relationship between maternal serum ferritin (SF) levels across pregnancy and the risk of gestational diabetes mellitus (GDM) in 17,560 women, of whom 12.3% were diagnosed with GDM. Elevated SF levels in both early (8.0–13.6 weeks) and late pregnancy (29.0–31.6 weeks) were independently and positively associated with increased GDM risk. Adjusted odds ratios (ORs) for GDM increased significantly across SF quartiles at both time points, with the highest quartile showing the greatest risk. Women with persistently high SF levels (upper 25th percentile at both time points) had the highest GDM incidence (15.3%), whereas those with initially high SF levels that decreased by late pregnancy had a reduced GDM risk. The study concludes that elevated SF levels are independently associated with GDM risk, raising concerns about routine iron supplementation for iron-replete pregnant women due to potential adverse effects on glucose metabolism.