Background: Neonatal hypoxic ischaemic encephalopathy (HIE) is the most common cause of encephalopathy in the neonatal period and carries a high risk of mortality and long-term morbidity.
Aim: The aim of this study was to investigate key antecedents of moderate and severe HIE in a large contemporary birth cohort.
Methods: A retrospective cohort study of births meeting criteria was conducted between 2016 and 2020 at the Mater Mothers' Hospital, Brisbane, Australia. This is a quaternary perinatal centre and Australia's largest maternity hospital. Univariate and multivariate Firth logistic regression were used to account for imbalanced frequency classes between non-HIE and HIE groups. Maternal variables and intrapartum factors were investigated for associations with neonatal moderate and severe HIE.
Results: Overall, 133 of 46 041 (0.29%) infants were diagnosed with HIE: 77 (0.17%) with mild HIE and 56 (0.12%) with moderate/severe HIE. Nulliparity, type 1 diabetes mellitus and maternal intensive care unit admission were associated with increased odds of moderate/severe HIE. Intrapartum risk factors included emergency caesarean birth, emergency caesarean for non-reassuring fetal status or failure to process, intrapartum haemorrhage and an intrapartum sentinel event (shoulder dystocia, cord prolapse, uterine rupture and placental abruption). Neonatal risk factors included male sex, late preterm gestation (35+0 -36+6 weeks), Apgar score less than four at 5 min, severe respiratory distress requiring ventilatory support and severe acidosis at birth.
Conclusions: This cohort study identified a series of potentially modifiable maternal and obstetric risk factors for HIE. Risk factors for HIE do not appear to have changed significantly with evolution in modern obstetric care.
Keywords: cerebral palsy; fetal distress; fetus; hypoxic ischaemic encephalopathy; intrapartum hypoxia; pregnancy.
© 2023 Royal Australian and New Zealand College of Obstetricians and Gynaecologists.