The effect of anemia on retinopathy of prematurity in extremely low birth weight infants

OBJECTIVE: Numerous risk factors for development of retinopathy of prematurity (ROP) in very low birth weight infants have been identified in the literature. However, the role of anemia in the development of ROP has not been adequately addressed. STUDY DESIGN: We retrospectively examined the medical records of all infants weighing ≤800 g who were admitted to a university hospital between July 1,1992 and December 30,1997. Highest and lowest hemoglobin and hematocrit values and the number of blood transfusions were recorded at each week of life during hospitalization. Gestational age at birth, birth weight, race, sex, oxygen status, history of bronchopulmonary dysplasia, length of hospital stay, and sepsis were also identified as potential risk factors. Data were analyzed using logistic regression to adjust for these confounding variables. RESULTS: Infants were grouped according to ROP status in the following manner: stage 0 to 1 ROP, stage 2 ROP, and stage 3 to threshold ROP. Sex, gestational age at birth, bronchopulmonary dysplasia, ventilator days, length of hospital stay, and number of blood transfusions were significantly associated with severity of ROP by univariate analysis. Using a logistic regression model, only gestational age (p=0.007) and number of blood transfusions ( p=0.04) remained statistically significant. CONCLUSIONS: Anemia did not affect severity of ROP as an independent risk factor. However, the number of blood transfusions did affect the highest stage of ROP in this group of premature infants. Infants who remained severely anemic (Hgb≤8 g/dl or Hct≤25%) for longer periods of time developed milder ROP than less anemic infants.