Incidence of retinopathy of prematurity in extremely premature infants over an 18-year period

Background: To report the incidence of retinopathy of prematurity (ROP) in a subgroup of extremely premature infants admitted to an Australian tertiary centre over an 18-year period.

Design: Retrospective study. Royal Brisbane and Women's Hospital Neonatal Intensive Care Unit.

Participants: Five hundred and fifty-four infants admitted between 23 and 25.6 weeks gestational age (GA).

Methods: The 18-year study was divided into three 6-year periods for analysis: period 1 (1992-1997), period 2 (1998-2003) and period 3 (2004-2009). Infants were compared based on their week of GA and by the study period in which they were born.

Main outcome measures: GA, birthweight, incidence and severity of ROP.

Results: Three hundred seventy-three (67.3%) infants survived until ROP screening, and 351 (63.4%) survived until discharge. ROP incidence increased from 78.2% in period 1 to 86.1% in period 3. Over the entire study, 90.5% of 23-week GA infants had ROP compared with 89.7% of 24-week GA infants and 76.1% of 25-week GA infants. Mean birthweight was significantly lower in infants with any ROP (725.1 g) and ROP of at least stage 3 (720.8 g) compared with infants without ROP (806.5 g) (P < 0.0001). Twenty-three-week GA infants had more severe ROP (28.6%) than 24 weeks (18.3%) and 25 weeks GA (11.9%).

Conclusions: There has been increased survival and incidence of ROP in extremely premature infants over the past 20 years. Lower birthweight and GA are both associated with higher incidence and more severe ROP.