ObjectiveTo observe and analyze the correlation between erythrocyte count and hemoglobin level in early life and retinopathy of prematurity (ROP). MethodsA clinical retrospective study. From January 2020 to December 2022, a total of 303 premature infants, who underwent fundus screening in Children's Hospital of Henan Province were included. There were 219 males and 84 females, with the average gestational age of (30.36±1.52) weeks and the average birth weight of (1 368.43±171.37) g. Early life was defined as 14 days after birth. According to the screening results, patients were divided into ROP group and no ROP group (control group). The results of red blood cell count, hematocrit and hemoglobin concentration of the two groups were compared and observed on the 3rd, 7th and 14th day after birth. The measurement data were compared by t-test, and the count data were compared by χ2 test. The risk factors of ROP were analyzed by logistic regression. The correlation between red blood cell count as well as hemoglobin concentration in early life and ROP was analyzed by receiver operating characteristics (ROC) curve. ResultsAmong the 303 premature infants screened, a total of 101 preterm infants were included in the ROP group, with the average gestational age of (30.39±1.48) weeks. And a total of 202 preterm infants were included in the control group, with the average gestational age of (30.35±1.55) weeks. There was no significant difference between the two groups in sex composition ratio (χ2=0.296) and gestational age (t=0.251) (P＞0.05). There were significant differences in birth weight (t=－2.024), blood transfusion times (U=－4.957), invasive mechanical ventilation duration (U=－2.215) and continuous positive airway pressure ventilation time (U=－5.224) between the two groups (P＜0.05). The incidence of periventricular leukomalacia (χ2=5.069), bronchopulmonary dysplasia (χ2=9.794) and sepsis (χ2=8.041) were significantly different (P＜0.05). The average hemoglobin level of patients in the ROP group on the 3rd, 7th and 14th day after birth were lower than those in the control group (t=－3.813, －2.753, －2.847; P＜0.05). Logistic regression analysis showed that low frequency of blood transfusion [odds ratio (OR)=1.241, 95% confidence interval (CI) 1.016-1.517] and short duration of continuous positive airway pressure (OR=1.128, 95%CI 1.031-1.234) were protective factors for ROP. The ROC curve analysis indicated that the abnormal threshold values of hematocrit and hemoglobin were the highest on the 14th day after birth, which were 115.5 g/L and 36.25% respectively. The sensitivities were 88.1% and 83.2%, respectively. ConclusionRed blood cell count and hemoglobin level in early life of preterm infants may have a certain correlation with the occurrence and development of ROP.