Gestational age references and trajectory of fetal haemoglobin in relation to outcome in neonates born before 30 weeks of gestation: a single-centre retrospective cohort study in The Netherlands

Summary: Background: Fetal haemoglobin (HbF) has a high oxygen affinity and predominates during fetal life. After birth, HbF is progressively replaced by adult haemoglobin (HbA). In preterm neonates, transfusion with HbA-containing red blood cells (RBCs) may accelerate this transition, increasing tissue oxygen exposure and oxidative stress, which have been associated with retinopathy of prematurity, bronchopulmonary dysplasia, and necrotizing enterocolitis. We aimed to establish gestational age (GA)-specific reference values and examine postnatal HbF trajectories in relation to transfusion exposure and outcomes, focusing on neonates born before 30 weeks’ gestation.