Bloody stool and necrotizing enterocolitis(NEC) is two main focus in non-neonatal intensive care unit ward and usually lead to longed duration of hospitalization.

Neutral temperature is a environmental temperature where the infant's body temperature is normal under resting state, and the changes of body temperature and skin temperature are less than 0.2-0.3 centigrade. According the definition, a suggested temperature range is set. For example, if an infant's body weight is more than 2500 gram, the initial set of environmental temperature is 31.3 centigrade with a range of 29.8-32.8 centigrade.

low environmental temperature is a risk factor for Bloody stool and NEC. Therefore, how to set the optimal environmental temperature is a challenge.

After birth, newborns must adapt to their relatively cold environment by the metabolic production of heat because they are not able to generate an adequate shivering response. Under the condition, environment temperature should be given to protect an infant from cold stress and cold injury, even NEC.

Therefore, the setting of the optimal environment temperature is a key focus in neonatal ward. Here, the investigators suggest a hypothesis that environment temperature should be set to keep warmth of extremities temperature and infant's body temperature is between 36.7-37.3 centigrade.

In the present study, the investigators will test the hypothesis.

Inclusion Criteria:

• body weight >2500 grams and/or gestational age >35 weeks
• an infant is diagnosed with hyperbilirubinemia and/or pneumonia without need for oxygen inhalation

Exclusion Criteria:

• congenital deformities
• refusal of parents' consent

an infant's body weight > 2500 grams and/or gestational age >35 weeks is included in the present study.