The etiology of retinopathy of prematurity appears to be multifactorial. Introduction of new treatments in neonatal care may add new risk factors. We have analyzed thc relationship between 42 perinatal factors and the development of retinopathy of prematurity in 78 infants with a birth weight<1501 g and/or gestational age<33 weeks. We have also applied a chronological analysis of the maximum and minimum pO2and pCO2values. Retinopathy of prematurity was seen in 37 of 78 infants (47.4%). Nineteen factors were found to be related to the development of retinopathy of prematurity. However, when step‐wise logistic regression analysis was used, only birth weight, number of days of oxygen therapy and use of beta‐blocking agents by the mother before birth were found to be associated with the development of retinopathy or prematurity. The results suggest that medication with beta blockers immediately before birth should be used cautiou