Objective  To relate umbilical artery blood gas parameters to mortality among neonates with hypoxic–ischaemic encephalopathy related to early onset seizures.

Design  Population cohort study.

Setting  British Columbia Women's Hospital.

Population  Forty-seven infants at ≥32 weeks of gestation admitted to NICU with early onset seizures secondary to hypoxic–ischaemic encephalopathy with umbilical artery blood gases done at delivery.

Methods  Patients were divided into two groups: (1) Infants with neonatal seizures who survived, and (2) infants with neonatal seizures who died related to hypoxic–ischaemic encephalopathy complications. Comparison of umbilical artery pH, PO2, PCO2, base deficit was done between the two groups with Student's t tests.

Main outcome measures  Umbilical artery pH, PO2, PCO2 and base deficit.

Results  The PO2 was significantly higher in the group that expired (18.36 ± 9.15 vs 12.33 ± 7.51). There were no significant differences in any other blood gas parameters between the groups.

Conclusion  Neither the umbilical artery pH nor base deficit is predictive of neonatal death in infants with hypoxic–ischaemic encephalopathy with seizures. The finding of a high PO2 in neonates who died may indicate an inability of those infants to efficiently extract oxygen from blood.