EPO and anemia (phenotype): Premature infants often develop severe anemia either early on secondary to iatrogenic blood loss from lab draws/procedures or later classically as anemia of prematurity, which is related to several factors, including insufficient erythropoietin production, immature bone marrow functions, high turnover of neonatal RBCs with shorter half-lives, infections, and nutritional deficiencies (74, 131).