Iron supplementation and gestational diabetes in midpregnancy.

Objective: Iron supplementation in pregnancy seems beneficial for neonatal/maternal outcomes, but it was associated with diabetes and hypertension in the general population.

Study Design: We investigated the association between iron supplementation during midpregnancy and metabolic/hypertensive abnormalities in 500 consecutive gestational diabetes mellitus (GDM) and 500 normoglycemic women.

Results: Iron-supplement users (n = 212/1000) showed significantly higher values of prepregnancy body mass index (BMI), actual BMI, waist circumference, blood pressure, fasting glucose, Homeostasis-Model-Assessment-Insulin-Resistance, and lower high-density lipoprotein-cholesterol than nonusers. The prevalence of GDM (70.8% vs 44.4%), hypertension (25.9% vs 9.8%), metabolic syndrome (25.9% vs 10.4%) was significantly higher in the former with a 2- to 3-fold-increased risk at multiple regression analyses. Most glucose values of the oral glucose tolerance test were significantly higher in iron supplemented women, both in GDM and normoglycemic individuals.

Conclusion: Iron supplementation is associated with glucose impairment and hypertension in midpregnancy; its potential harmful effects might be carefully debated regarding its effectiveness.