EPO and anemia (phenotype): Anemia of prematurity (AOP) is a hypo-regenerative, normocytic, normochromic anemia that appears between the second and sixth weeks of life and is characterized by multiple factors, including reduced serum erythropoietin (EPO) levels, iatrogenic blood loss, hemorrhage, hemolysis, hypovolemia, insufficient erythropoiesis, and reduced red blood cell (RBC) survival [1,2].