ObjectiveTo investigate the incidence and risk factors of retinopathy of prematurity (ROP) in extremely preterm infants (EPI) before 28 weeks of gestation during 8-years period.MethodsA retrospective study. From January 1, 2011 to December 31, 2018, 300 EPI infants with a gestational age of less than 28 weeks admitted to the neonatal intensive care unit (NICU) of Tianjin Central Hospital of Gynecology Obstetrics were included in the study. EPI birth gestational week (GA), birth weight (BW), gender and other basic information, as well as neonatal respiratory distress syndrome, oxygen (≥10 d), bronchopulmonary dysplasia (BPD) and other hospitalizations and complications were recorded. According to ROP international classification standards, ROP was staged. Severe ROP was defined as ROP that requires treatment. The screening start time, screening interval, and intervention time of all children tested were carried out in accordance with the requirements of the “Guidelines for Screening Retinopathy of Prematurity” until the end of follow-up. The most severe ROP during the follow-up of each examined child was recorded as the final screening result of the examined child, and those with asymmetric eyes with the screening results of the severe side of the diseas was recorded. A retrospective analysis of the overall incidence of EPI ROP showed the incidence of severe ROP, and the first and second stages of EPI ROP during the 8 years (from January 1, 2011 to December 31, 2014, and January 1, 2015 to December 31, 2018), changes in the rate of severe illness. Logistic regression analysis was used to screen independent risk factors for severe ROP.ResultsAmong 300 EPI infants, the average GA was (26.7±1.8) weeks; the average BW was (993.3±178.7) g. Two hundred and five infants (68.3%) were diagnosed with ROP, 116 (56.6%), 57 (27.8%), and 32 (15.6%) infants of stage Ⅰ, Ⅱ, and Ⅲ disease, respectively. There were no infants of stage IV and V. There were 30 infants (14.6%) with additional lesions and 59 infants (19.7%) with severe ROP requiring treatment. With the increase of GA (χ2=52.391, 44.521; P=0.000, 0.000) and BW (χ2=43.772, 26.138; P=0.000, 0.000), the incidence of EPI ROP and the incidence of severe ROP decreased significantly. From 2011 to 2018, the number of people surviving EPI obviously increased, especially those with small GA (26 weeks) and low BW (750 g). The average GA of the second stage EPI was lower than that of the first stage, the difference was statistically significant (t=2.243, P=0.026); the average BW of the second stage EPI was lower than the first stage, the difference was not statistically significant (t=1.428, P=0.154). The incidence of ROP in the second stage EPI was slightly higher than that in the first stage, and the incidence of severe ROP was lower than that in the first stage, the difference was not statistically significant (χ2=1.069, 1.723; P=0.301, 0.189). Multivariate logistic regression analysis showed that GA＜27 weeks (β=－2.584, P=0.032), maternal chorioamnionitis (CA) (β=－0.935, P=0.038) and BPD (β=－1.432, P=0.001) was an independent risk factor for severe ROP.ConclusionsThe incidence of EPI ROP and severe ROP are 68.3% and 19.7%, respectively. From 2011 to 2018, the number of survivors of EPI obviously increase, and those with small GA and low BW increase significantly; however, the incidence of ROP and severe ROP remaine stable. GA, CA and BPD are independent risk factors for severe ROP.