Purpose: To calculate incidence and evaluate the risk factors of the threshold retinopathy of prematurity (ROP) in very low birth-weight (VLBW, birth weight less than 1,251 gram) infants. We also compared the incidence of threshold ROP in Taiwan with those of Caucasians and Negros. Additionally, the post-conception age when threshold ROP happened was considered.
Methods: From February 1995 to February 2000, we enrolled 458 VLBW infants at the China Medical College Hospital. Patients with congenital anomalies and those who survived less than 6 months were excluded. The perinatal and neonatal data of enrolled infants were reviewed. Student's t test and chi-square test were used to evaluate the statistical significance of risk factors. We also used logistic regression test and correct classification rate to evaluate different risk factors.
Results: The incidence of threshold ROP in our study was 6.8%. The gestational age (GA), birth weight (BW), number of days in using ventilator, continuous positive airway pressure (CPAP) and oxygen supplements, the occurrence of broncopulmonary dysplasia (BPD), respiratory distress syndrome (RDS), periventricular leukomalacia (PVL), necrotizing enterocolitis (NEC) and the length of hospitalization were statistically different between patients groups with and without threshold ROP (p < 0.05). However, small size for gestational age (SGA), sepsis status, intraventricular hemorrhage (IVH) status (Gr.III and Gr.IV) and type of delivery were not significantly different between patients with and without threshold ROP (p > 0.05). Threshold ROP was noted at an average post-conception age of 34.25 weeks.
Conclusions: The incidence of threshold ROP (6.8%) in VLBW Taiwan babies is comparable with the incidence of Caucasian patients in Western countries. Risk factors including PVL, NEC, BPD and RDS should be avoided to prevent the occurrence of threshold ROP. Threshold ROP occurred at an average of 34.3 weeks of post-conception age; the premature baby around this age must be checked carefully.