The investigators will analyse the raw ECG using Matlab® with in-house algorithms to quantify specific linear and non-linear measures of HRV. All recruited encephalopathic babies will have brain magnetic resonance (MR) imaging and spectroscopy using harmonised protocols and neurodevelopmental assessment, as a part of clinical care, or as a part of MR biomarker studies. This data will be collected and used for the Heartbeat study to examine the association between heart rate variability with brain injury and neurodevelopmental outcome.