Supplementary Material for: Magnetic Resonance Biomarkers and Neurological Outcome of Infants with Mild Hypoxic-Ischaemic Encephalopathy Who Progress to Moderate Hypoxic-Ischaemic Encephalopathy

<b><i>Background:</i></b> There is increasing concern that infants with mild hypoxic-ischaemic encephalopathy (HIE) may develop seizures and progress to moderate HIE beyond the therapeutic window for cooling. <b><i>Objective:</i></b> The aim of this study was to examine the effect of therapeutic hypothermia on magnetic resonance imaging (MRI) biomarkers and neurological outcomes in infants with mild HIE and seizures within 24 h after birth. <b><i>Methods:</i></b> This study shows an observational cohort study on 366 (near)-term infants with mild HIE and normal amplitude-integrated electroencephalography background. <b><i>Results:</i></b> Forty-one infants showed progression (11.2%); 29/41 (70.7%) were cooled. Infants with progression showed cerebral metabolite perturbations and higher white matter injury scores compared to those without in both cooled and non-cooled groups (<i>p</i> = 0.001, <i>p</i> = 0.02). Abnormal outcomes were seen in 5/12 (42%) non-cooled and 7/29 (24%) cooled infants with progression (<i>p</i> = 0.26). <b><i>Conclusions:</i></b> Early biomarkers are needed to identify infants with mild HIE at risk of progression. Mild HIE infants with progression showed a higher incidence of brain injury and abnormal outcomes.