In the following of the reduction of Hb in infants with ROP, their RBC production increased consequently; therefore, the percentage of reticulocytes in ROP patients was significantly higher than normal infants (3.97±2.53 x106cell/μl and 3.09±2.08 x106cell/μl, respectively, P=0.015). This evidence concerns the gene GSTM1 and retinopathy of prematurity.