EPO and anemia (phenotype): Premature infants typically develop severe anemia either within the first few weeks due to phlebotomy losses, or later, beyond 4 weeks due to the classical anemia of prematurity, which is a multifactorial process related to hypoactivity of the immature bone marrow, insufficient erythropoietin production, high turnover of neonatal RBCs, rapid somatic growth, and nutritional deficiencies64.