Supplementary Material for: Neonatal Hemoglobin Levels in Preterm Infants Are Associated with Early Neurological Functioning

Background: Neonatal anemia may compromise oxygen transport to the brain. The effects of anemia and cerebral oxygenation on neurological functioning in the early neonatal period are largely unknown. Objective: This study aimed to determine the association between initial hemoglobin levels (Hb) and early neurological functioning in preterm infants by assessing their general movements (GMs). Methods: A retrospective analysis of prospectively collected data on preterm infants born before 32 weeks of gestation was conducted. We excluded infants with intraventricular hemorrhage > grade II. On day 8, we assessed infants’ GMs, both generally as normal/abnormal and in detail using the general movement optimality score (GMOS). We measured cerebral tissue oxygen saturation (r_cSO₂) on day 1 using near-infrared spectroscopy. Results: We included 65 infants (median gestational age 29.9 weeks [IQR 28.2–31.0]; median birth weight 1,180 g [IQR 930–1,400]). Median Hb on day 1 was 10.3 mmol/L (range 4.2–13.7). Lower Hb on day 1 was associated with a higher risk of abnormal GMs (OR = 2.3, 95% CI: 1.3–4.1) and poorer GMOSs (B = 0.9, 95% CI: 0.2–1.7). Hemoglobin strongly correlated with r_cSO₂ (rho = 0.62, p < 0.01). Infants with lower r_cSO₂ values tended to have a higher risk of abnormal GMs (p = 0.06). After adjusting for confounders, Hb on day 1 explained 44% of the variance of normal/abnormal GMs and r_cSO₂ explained 17%. Regarding the explained variance of the GMOS, this was 25% and 16%, respectively. Conclusions: In preterm infants, low Hb on day 1 is associated with impaired neurological functioning on day 8, which is partly explained by low cerebral oxygenation.