Incidence and severity of retinopathy of prematurity in extremely premature infants

Objective: To analyze incidence and severity of retinopathy of prematurity (ROP) among extremely premature infants. Design: Retrospective, longitudinal study. Participants: We studied the data concerning 207 infants whose gestational ages (GAs) were equal to 27 weeks or fewer and who were admitted to a neonatal intensive care unit between July 2006 and July 2010. Methods: Data were extracted from the Canadian Neonatal Network, which maintains clinical information about neonates, and were confirmed by reviewing medical charts. Infants were classified into 2 groups: the GAs of the infants in group 1 were <= 25 weeks; those in group 2 had GAs between 26 and 27 weeks. The incidence and severity of ROP were assessed in the total screened population and between groups. Results: The overall incidence of any ROP was 64.7%; 88% of infants in group 1 had any ROP compared to 48% infants in group 2. The overall incidence of type 1 ROP was 11.6%; in group 1 it was 24.4%, compared to 2.5% in group 2. Type 1 ROP was significantly associated with birth weight in grams (p < 0.001; OR = 8.20) and GA (p < 0.001; OR = 2.46). There was no difference in mean postmenstrual age at first ROP onset between group 1 and group 2 (33.5 vs 33.9 weeks, respectively). PMA at time of ROP diagnosis was not associated with development of type 1 ROP (p = 0.75; OR = 0.94; Cl 0.62-1.41). Conclusions: Extremely premature infants with lower GA had a higher incidence of type 1 ROP. Earlier presentation of ROP did not predict development of type 1 ROP. No infant with a GA > 26 weeks at birth or birth weight > 1000 g had type 1 ROP.