155 - Nucleated Red Blood Cell Count at Birth and Volume of RBC Transfused are Both Associated with the Risk of Developing Retinopathy of Prematurity

Publication Number: 2149.155

Bailey B. Zeiler, University of Utah School of Medicine, Salt Lake City, UT, United States; Timothy M. Bahr, University of Utag, Provo, UT, United States; Robin K. Ohls, University of Utah School of Medicine, Salt Lake City, UT, United States; Robert D.. Christensen, University of Utah and Intermountain Health, Salt Lake City, UT, United States; M.Elizabeth R. Hartnett, Stanford University School of Medicine, SAN CARLOS, CA, United States

Background: The nucleated red blood cell count (NRBC), measured at or shortly after birth, has been reported to be a biomarker of fetal hypoxia. Other studies described an association between the NRBC count within 6 hours of birth and the risk of subsequently developing retinopathy of prematurity (ROP). However, differences in study designs make conclusions tenuous. Other studies correlated red cell transfusions with ROP incidence. We are not aware of any studies that examined both NRBC count and RBC transfusions (in the same cohort) on ROP risk.

Objective: To assess the association between NRBC count at preterm birth and occurrence of ROP, as well as the association between the number and volume of RBC transfusions received and ROP occurrence.

Design/Methods: We retrospectively analyzed all infants in the Intermountain Health NICUs born < 32 weeks' gestation between January 2021 and December 2024 who had an NRBC count within 6 hours after birth and retinal examinations for ROP.

Results: We analyzed 368 infants, and found a robust positive association between absolute NRBC count (NRBCs per microliter of blood) and ROP incidence and severity. After controlling for birthweight, gestational age, and mechanical ventilation at 14 days of life, the NRBC count at birth was an independent risk factor for severe ROP (p=0.003). For every 1000 cells/µL increase in the NRBC count at birth, the risk of subsequently developing severe (grade≥3) ROP increased by 6.8% (95% C.I 3.0 - 10.0%). The number of RBC transfusions and the volume of RBC transfusions/kg birthweight were also associated with ROP incidence and severity (all p< 0.001). Infants who did not develop ROP were more likely to have received no RBC transfusions. However, neither factor alone (elevated NRBC count at birth or RBC transfusion) was necessary or sufficient for ROP.

Conclusion(s): The absolute NRBC count at preterm birth can help risk-stratify infants for ROP. The NRBC count at birth and the volume of RBC transfusions both influence the risk of ROP severity. Reducing or eliminating RBC transfusions, especially in those with an elevated NRBC count at birth, might reduce the incidence of severe ROP.

Figure 1. Higher NRBC Counts are Observed in Infants with Severe ROP Across Gestational Age Groups


Table 1. The NRBC count at birth and volume of RBC transfusions both influence the risk of ROP severity
ROP, retinopathy of prematurity; PMA, post-menstrual age; RBC, red blood cell; Tx, transfusion; n = number of transfusions received
*Median and 25-75 percentiles
**Volume of RBC and platelet transfusion/kg were calculated based on birth weight

Table 2. Reducing or eliminating RBC transfusions, especially in those with an elevated NRBC count at birth, might reduce incidence of severe ROP
NRBC, nucleated red blood cell; ROP, retinopathy of prematurity; RBC, red blood cells; Tx, transfusion; n, number; kg, kilogram birth weight