To study the relationship between blood transfusion, iron load and retinopathy of prematurity (ROP), we performed a prospective observational cohort study in a level III neonatal intensive care unit. During a 24-month period, data on the volume of blood transfused during the first 6 weeks of life and on the incidence of ROP were collected in all surviving very low birth weight infants (n = 114; median birth weight 1130 g. range 520-1500 g). Associations between these data and values for serum iron, transferrin and ferritin measured at weekly intervals were analysed in a nested case-control design by logistic regression. There was a significant association between the volume of blood transfused and the incidence of ROP. After adjustment for gestational age at birth, duration of oxygen therapy (FiO2 > 0.3) and duration of mechanical ventilation, the relative risk of developing ROP was 6.4 (95% CI 1.2-33.4) for infants who had received 16-45 ml/kg, and 12.3 (1.6-92.5) for those who had received more than 45 ml/kg of blood (reference, 0-15 ml/kg). In contrast, there was no independent relationship between ROP and any of the parameters on iron metabolism analysed.
Conclusion: This study confirms the role of blood transfusions as an independent risk factor for ROP. This relationship, however, does not appear to be mediated via an increased iron load.