Iron Deficiency Screening with Reticulocyte–Hemoglobin Content and 2-Year Neurodevelopmental Outcomes in Extremely Low Birth Weight Infants

The objective of this study is to assess reticulocyte–hemoglobin (RET–He) and daily iron dosing with 2-year cognitive outcomes. A multicenter retrospective cohort study of 78 infants born between 2014 and 2018 at less than 28 weeks' gestation or less than 1,250 g birth weight throughout level III or IV neonatal intensive care units (NICUs). RET–He measurement, iron supplementation, and the Bayley Scales of Infant and Toddler Development-III (Bayley-III) test were analyzed using multiple linear regression models. For every 1 mg/kg increase in mean total daily iron supplementation, the Bayley-III cognitive score increased by 2.9 points (95% confidence interval [CI]: 0.4–5.4, p = 0.023). No associations were identified between minimum or maximum RET–He and Bayley-III cognitive outcomes. Infants with a RET–He value < 29 pg tended to be 2.53 times more likely to have a Bayley-III language score below 70 (odds ratio: 2.53, 95% CI: 0.92–6.95, p = 0.071). Thirty-eight out of 78 (38.4%) infants were iron-deficient during their NICU hospitalization, with at least one RET–He < 29 pg. An association was identified between a higher mean daily iron dose and improved cognitive outcomes for infants, but not between the iron index RET–He and neurodevelopmental outcomes. Iron deficiency remains common among NICU patients undergoing follow-up, suggesting that standard iron dosing may be inadequate for high-risk neonates.