Newborns are uniquely at risk of abnormal body temperature, and susceptible to the potential ill effects of both hypo- and hyperthermia. Building on the understanding of the causes of temperature alteration and the physiologic mechanisms to prevent it, this review explores how both low and high body temperature may lead to severe injury, illness, or death. Support and regulation of the thermal environment of the newborn has long been recognized as a critical aspect of newborn care, and it has become increasingly important as smaller and less mature infants are able to survive. Because of their even more limited capacity for self-protection compared with term infants, the most immature infants can readily lose heat and body temperature, and succumb to the severe physiologic consequences of hypothermia. Hyperthermia, although much less common, may also have profound negative impact on the newborn, and in some ways poses a greater risk to term and late preterm infants.
A variety of different methods are discussed as means to reduce heat loss from evaporation, convection, conduction, or radiation and protect an infant from hypothermia. A number of these modalities are specifically geared to the critical time period immediately after birth, including occlusive plastic wraps, exothermic mattresses, and augmented room temperatures. In other cases, such as the use of hats, the value extends from birth through the days immediately after, and still other care practices are primarily designed for use in the NICU or nursery. The effectiveness, advantages, and drawbacks of these different modalities are outlined.