Deficiency, iron: An inadequate amount of iron, the most common known form of nutritional disorder in the world. Iron is necessary to make hemoglobin, the molecule in red blood cells that transports oxygen. Iron deficiency results in anemia. The prevalence of iron deficiency is highest among young children and women of childbearing age (particularly pregnant women). In pregnant women, iron deficiency increases the risk for preterm delivery and delivery of babies with low birth weight. In children, iron deficiency causes developmental delays, behavioral disturbances, failure to thrive, and increased infections. The treatment of iron deficiency anemia includes using iron supplements and iron-containing foods in the diet. Food sources of iron include meat, poultry, eggs, vegetables, and cereals (especially those fortified with iron). However, iron supplements should not be given to children unless a physician recommends them.