Erythropoiesis decreases dramatically after birth as a result of increased tissue oxygenation and a reduced production of erythropoietin . In healthy term infants, hemoglobin levels are high (>14 g/dL) at birth and then rapidly decline, reaching a nadir of approximately 11 g/dL at six to nine weeks of age, which is called "physiologic anemia of infancy" (also called the "physiologic nadir") (figure 1) [3,4]. Normal values for hematocrit and hemoglobin during the first year of life in healthy term infants Data from: 1. Jopling J, Henry E, Wiedmeier SE, et al. Reference ranges for hematocrit and blood hemoglobin concentration during the neonatal period: data from a multihospital health care system. Pediatrics 2009; 123:e333. 2. Oski FA, Naiman JL. Hematologic problems in the newborn, 2nd ed, WB Saunders, Philadelphia 1972; p.13. 3. Saarinen UM, Siimes MA. Developmental changes in red blood cell counts and indices of infants after exclusion of iron deficiency by laboratory criteria and continuous iron supplementation. J Pediatr 1978; 92:412.