Outcomes in children after mild neonatal hypoxic ischaemic encephalopathy: A population-based cohort study

To investigate whether mild neonatal hypoxic ischaemic encephalopathy (HIE) in term born infants is associated with cerebral palsy, epilepsy, mental retardation and death up to 6 years of age. Population-based cohort study. Sweden, 2009-2015. Live term born infants without congenital malformations or chromosomal abnormalities (n = 505 075). Birth and health data were retrieved from Swedish national health and quality registers. Mild HIE was identified by diagnosis in either the Swedish Medical Birth Register or the Swedish Neonatal Quality Register. Cox proportional hazards regression was used to estimate hazard ratios (HRs) with 95% confidence intervals (CIs). A composite of the outcomes cerebral palsy, epilepsy, mental retardation and death up to 6 years of age. Median follow-up time was 3.3 years after birth. Of 414 infants diagnosed with mild HIE, 17 were classified according to the composite outcome and incidence rates were 12.6 and 2.9 per 1000 child-years in infants with and without HIE respectively. Infants with mild HIE was four times as likely to be diagnosed with the composite outcome (HR 4.42, 95% CI 2.75-7.12) compared with infants without HIE. When analysed separately, associations were found with cerebral palsy (HR 21.50, 95% CI 9.59-48.19) and death (HR 19.10, 95% CI 7.90-46.21). HRs remained essentially unchanged after adjustment for covariates. Mild neonatal HIE was associated with neurological morbidity and mortality in childhood. Challenges include identifying infants who may develop morbidity and how to prevent adverse outcomes.