Body Temperature of Newborns: What is Normal?

Abstract

Medical records of 203 healthy full-term infants were reviewed to determine the range of axillary temperatures for newborn infants, factors that affect temperature and nursery management of infants with temperatures outside published normal ranges. The mean birth temperature was 36.5⁰C (S.D. = 0.6⁰C). Temperature was associated with birth weight (p<0.0005) and the presence of maternal fever (p<0.0001) but not with type of environment or time of birth. The mean temperature increased with age, rising 0.2⁰C by 2-3 hours after birth (p<0.0001) and 0.3⁰C by 15-20 hours (p<O.OOOl). Among a subset of 114 eligible neonates the mean temperature dropped 0.2⁰C after bathing (p<0.0001). Although 17% of all temperatures measured were in the hypothermic (<36.3⁰C) range, the only response recorded by nursery staff consisted of warming by modifying the environment, e.g., bundling. Blood cultures were drawn from 51 infants (25%), 43 because of maternal intrapartum antibiotic treatment for maternal fever or prolonged duration of ruptured amniotic membranes (>24 hours) and none for evaluation of abnormal temperatures. No infants had systemic infections and all were discharged in stable condition. Newborn axillary temperatures in our nursery were considerably lower than what has been previously described as "normal." Given the frequency of "hypothermia" and absence of associated illness, we believe the reference range for newborn temperatures should be expanded to include lower temperatures.