Gestational diabetes mellitus (GDM), defined as hyperglycemia with blood glucose values above normal but below those diagnostic of DM, and iron deficiency (ID) with or without anemia (IDA) are common during pregnancy. Both disease patterns are associated with an increased risk of complications during pregnancy and at delivery and may have a variety of negative effects on different aspects of child development. Thus, GDM and ID/IDA during pregnancy should be prevented. Whether iron supplementation with high oral doses acutely increases hepcidin during pregnancy, and whether this acute iron-induced increase in hepcidin decreases insulin sensitivity, is uncertain.