Andersen M, et al. - Researchers performed this investigation to systematically examine whether the severity of hypoxic ischemic encephalopathy (HIE) during the first week of life is correlated with heart rate variability (HRV) [describes the variation of time intervals between each subsequent heartbeat] measures. Participants in the study were 248 neonates. According to the findings, the strength of evidence was very low for all HRV measures. Neonates with severe or moderate HIE exhibited a decrease in most HRV measures vs neonates with mild or no HIE with a greater decline in those with severe HIE. Overall, the authors concluded that most HRV measures were correlated with moderate and severe HIE. Consequently, during the first week of life, HRV is a potential biomarker for HIE severity. The uncertainty, however, requires more research.