Introduction Recent technological advances in neonatology have increased the survival rate of very low birth weight infants, which has led to a correspondingly increased incidence of retinopathy of prematurity (ROP).

Objective To identify neonatal risk factors for severe ROP in premature babies.

Methods A retrospective cohort study was undertaken In Shiraz from January 2006 to April 2010. All premature neonates with gestational age (GA) of <34 weeks or birth weight (BW) of <2000 g were included in the study.

Results During 5 years of study, 1095 premature infants were analysed. There were 732(66.8%) infants did not develop ROP, 363(33.2%) infants presented with various degrees of ROP (249 infants without treatment and 114 infants were treated with laser). We compared 2 groups of neonates, who were treated with laser and those who didn't received any treatment. Univariate logistic regression showed that GA [OR=0.68 (95% CI 0.62 to 0.75)], BW [OR=0.997 (95% CI 0.996 to 0.998)], length [OR=0.84 (95% CI 0.80 to 0.89)], and head circumference (HC) [OR=0.73 (95% CI 0.66 to 0.80)] had significant inverse relationships with developing ROP and there is no statistical relationship between sex of neonates and ROP (p value=0.054). However, after adjustment in multivariate logistic model, only GA and HC remained in the model as independent risk factors. Adjusted OR for H.C was 0.8 (95% CI 0.71 to 0.90) and Adjusted ORs for, GA ≤28 weeks, and, 28 weeks<GA<32 weeks, were 4.32 (95% CI 1.76 to 10.57) and 3.5 (95% CI 1.56 to 7.83) in comparison with ,GA≥32 weeks.

Conclusion Gestational age and head circumference at birth were the most important risk factors for severe ROP in our study.