hypothermia is a core temperature < 35 to 35.5° C. The condition may be purely environmental or represent intercurrent illness. Treatment is rewarming and correction of the cause.
Normal rectal temperature in term and preterm infants is 36.5 to 37.5° C. Although hypothermia is a core temperature < 35 to 35.5° C, there is cold stress at higher temperatures whenever heat loss requires an increase in metabolic heat production.