Introduction An elevated white cell count in term newborns with neonatal encephalopathy (NE) has been associated with increased risk of mortality and neurological disability.

Aims To examine the associations between the white blood cell (WBC) indices of severely asphyxiated infants and mortality/neurodevelopmental outcome at 2 years.

Methods 69 infants with NE were randomized to normothermia or hypothermia as part of the TOBY trial. Serial WBC parameters, clinical outcome and 2-year developmental assessments were evaluated in 62 infants.

Results There were 46 survivors, 16 non-survivors. 43 infants received hypothermia therapy and the remainder (n=19) kept normothermic. Elevated WBC count and Granulocyte count at 0–8 hours predicted mortality. ROC analysis favours Granulocyte count as the superior predictor of mortality. For each unit increase in WBC count the odds ratio of death increases by 1.076 for the normothermic group (p=0.032) but not for the hypothermic group (p=0.290). High leukoycte counts at 20–28 hours (range 1–27 × 10⁹/L) are associated with worsening motor scores (p<0.0001) and with abnormal motor outcome.

Conclusion Elevated WBC counts increase the risk of mortality in the normothermic group but not in the hypothermic group. Raised leukocyte counts at 20–28 hours are associated with abnormal motor outcome at 2 years. WBC counts may play a future role in a biomarker panel helping to predict outcome following neonatal hypoxic-ischaemia.