Group 1 (Cooled group) Cooling procedure We will fit a cooling cap (Olympic Medical Cool Care System, Olympic Medical) around the head for 72 h. The system consists of a small thermostatically controlled cooling unit with a pump that circulated water through the cap. The initial water temperature is set between 8°C and 12°C. All infants will be nursed under a radiant overhead heater, which is servo-controlled to the infant's abdominal skin temperature and adjusted to maintain the rectal temperature at 33.5-34.5ºC. Adjustments will be made to the cooling cap water temperature to stay within these limits. At the start of hypothermia, the overhead heater will be turned off for 20-30 min to accelerate cooling, and then turned back on once the rectal temperature had fallen to 35.5ºC.