Anemia prevalence is highest in preschool children, women of reproductive age, and women who are pregnant. While the etiology of anemia is multifactorial, iron deficiency is the most commonly recognized nutritional cause. Observational studies imply that supplementation with iron or iron-folic acid should be started early in pregnancy, if not before, in order to prevent low-birth-weight and preterm delivery. Despite this, findings from clinical trials, even those conducted during early pregnancy, are equivocal. Recent follow-up studies of children born to women supplemented with iron-folic acid suggest that mortality is decreased and that the infant's iron endowment reflects the mother's iron status during pregnancy.