Neonatal encephalopathy requiring therapeutic hypothermia over 5 years in a national Irish birth cohort: Relevance of the obstetric data.

BACKGROUND

Neonatal encephalopathy, often due to peripartum hypoxia-ischemia, remains a significant cause of neonatal morbidity and mortality. Therapeutic hypothermia is the established treatment for moderate and severe neonatal encephalopathy in Ireland since 2012 after publication of an international trial. Despite adherence to strict clinical criteria, the maternal and obstetric factors associated with infants requiring therapeutic hypothermia remain incompletely understood.

OBJECTIVES

To describe maternal and infant characteristics among infants treated with therapeutic hypothermia in Ireland over five years, and to assess whether obstetric factors are associated with increased risk of neonatal encephalopathy.

STUDY

DESIGN

A population-based, retrospective cohort study of all infants (n = 357) who received therapeutic hypothermia in Ireland from 2016 to 2020 was conducted. Data were collected from 19 maternity units and compiled into a national register. The study compared antenatal and intrapartum characteristics between therapeutic hypothermia cases and the national birthing population. Risks per 1,000 births and their exact Poisson 95% confidence intervals and risk ratios (RR) and their 95% CI were the primary statistical measures reported.

RESULTS

The incidence of therapeutic hypothermia was 1.18 per 1,000 live births (357/301,442), with some evidence of increase over time (RR for 2020 vs 2016 = 1.36, CI: 0.98-1.90; p = 0.068). Infants born to nulliparous women had a more than twofold higher risk of receiving therapeutic hypothermia (1.79 vs 0.80 per 1,000; RR = 2.25, CI: 1.82-2.77; p < 0.001). Therapeutic hypothermia risk increased significantly with maternal obesity (RR = 1.65) and fetal growth restriction (RR = 2.74 for < 3rd centile; RR = 1.99 for 4th-10th centile). Emergency caesarean section was associated with the highest therapeutic hypothermia risk. Sentinel events such as shoulder dystocia (n = 42; 11.8%), placental abruption (n = 20; 5.6%), and uterine rupture (n = 12; 3.4%) were significantly associated with therapeutic hypothermia (shoulder dystocia RR = 17.48, CI: 12.67-24.12; p < 0.001). Overall, 14% (50/357) of infants died. Among those followed up with Bayley-III testing (n = 85), 21.2% had motor, 16.5% cognitive, and 28.2% language delays.

CONCLUSION

Infants born to nulliparous women, those exposed to maternal obesity, fetal growth restriction and emergency caesarean section birth were at increased risk of requiring therapeutic hypothermia. Sentinel events, while strongly associated with therapeutic hypothermia, were infrequent, suggesting cumulative or dynamic perinatal factors play a critical role. These findings underscore the importance of enhanced intrapartum monitoring and structured clinical response systems to reduce avoidable neonatal encephalopathy cases in Ireland.