PURPOSE To investigate the effect of hemoglobin F (HbF) and hemoglobin A (HbA) levels on development of retinopathy of prematurity (ROP) in premature infants. METHODS In this prospective study, blood samples were collected from the side of the heel of 49 premature infants at postnatal months 0, 1, 2, and 3. HbF and HbA levels were measured in all samples and analyzed statistically. Furthermore, correlation analysis was performed regarding development of ROP, blood transfusion, and HbF and HbA levels. RESULTS A total of 49 infants were included. The mean gestational age of the premature infants was 30.9 +/- 2.7 weeks (range, 25-35 weeks); mean birth weight, 1542 +/- 582 g (range, 520-3240 g). Of the 49 premature infants, stage 1 ROP or above developed in 26 (53%). Mean HbF levels were lower at postnatal months 1 and 2 in premature infants with ROP compared to those without ROP (P = 0.013 and 0.02, respectively); however, mean HbA levels were higher in the infants with ROP than the others (P = 0.034 and 0.029, respectively). Analysis of covariance that ignored transfusion revealed no difference between the means of Hb variants in the infants with and without ROP (P = 0.572 and 0.486). CONCLUSIONS Blood transfusion significantly altered the levels of HbF and HbA in premature infants, and Hb variants have no direct effect on development of ROP.