Iron homeostasis in pregnancy and spontaneous abortion

During pregnancy, iron requirements are increased to support maternal erythropoietic expansion and fetal growth and development. To meet these requirements, dietary iron absorption increases, and available iron stores are mobilized. These adjustments are thought to be in large part mediated by the iron-regulatory hormone hepcidin, which controls the concentrations of ferroportin, the sole exporter of iron into the extracellular fluid and blood plasma. Hepcidin regulation of iron availability during healthy and abnormal pregnancies is not well understood. In our cross-sectional study, we compared hepcidin, iron and hematological parameters between nonpregnant control women, healthy pregnant women in the first and second trimester, and women with spontaneous abortion in the first trimester. We found that in healthy pregnancy, hepcidin increased in the first trimester compared with nonpregnant women, but then decreased during the second trimester. The second trimester hepcidin levels decreased despite stable serum iron concentrations, suggesting active suppression of hepcidin, presumably to enhance iron availability as iron demand increases. In women with spontaneous abortion during the first trimester, hepcidin, serum iron, and ferritin concentrations were all increased compared with the first trimester healthy pregnancy. Although the specific mechanisms remain to be determined, our findings demonstrate that maternal hepcidin is regulated by signals related to the progression of pregnancy, and that pregnancy loss is associated with profound changes in maternal iron metabolism. These observations highlight the existence of fetoplacental signals that modulate maternal iron homeostasis.