At a univariate analysis, ROP was significantly associated with gestational age, body weight, intraventricular hemorrhage, patent ductus arteriosus, bronchopulmonary dysplasia, erythropoietin therapy and sepsis, while AP-ROP was significantly associated with gestational age, bronchopulmonary dysplasia, and sepsis. This evidence concerns the gene EPO and Intraventricular hemorrhage.