Duration of oxygen therapy and exchange transfusion as risk factors associated with retinopathy of prematurity in very low birthweight infants.

One hundred and thirteen consecutive infants with a very low birthweight of less than 1500 g were followed prospectively for 6 months to determine the incidence of retinopathy of prematurity (ROP) and associated risk factors. Of this group, 36 (31.9%) infants developed ROP (13 infants had stage 1 ROP, nine had stage 2, six had stage 3, six had stage 4, and two had cicatricial stage ROP). Stepwise logistic regression analysis of various potential risk factors (birthweight, gestation, duration of oxygen therapy, duration of ventilation, highest documented PaO2 and exchange transfusion) showed that only two risk factors were significantly associated with the development of ROP. These risk factors were: the duration of oxygen therapy (p = 0.0005) and exchange transfusion during the neonatal period (odds ratio 5.754, 95% confidence interval 1.002 to 32.997, p = 0.049). The equation of the regression model is: log (odds of developing ROP) = -0.8395 + 0.1447 (OXY)- 0.8750 (ET), where OXY is the duration of oxygen therapy in days, ET = -1 when there was a history of exchange transfusion, and ET = 1 when there was no history of exchange transfusion.