The placenta is a heat exchanger which transfers heat generated by metabolism from fetus to mother. After birth the newborn infant functions as a homeotherm, maintaining deep body temperature at 37°C. Heat control places a large demand on neonatal metabolism and physiology because a large surface area to volume ratio and wet skin make the newborn baby vulnerable to excessive heat loss.
Newborn infants have a specialized organ for heat production: brown adipose tissue, which allows non-shivering thermogenesis. Catecholamines are released in response to cold, stimulating oxidative phosphorylation in these cells, where uncoupling energy metabolism from ATP generation allows chemical energy to be converted into heat. Non-shivering thermogenesis is impaired in the first few hours of life in sick infants and after maternal sedative administration.
Despite this, the newborn infant has a limited capacity to maintain core temperature. At environmental temperatures below 32° C non-shivering thermogenesis increases oxygen consumption and maintains core temperature. However, at environmental temperatures below 24°C heat production is inadequate and the body temperature will fall. It is therefore important to ensure the environmental temperature in delivery rooms and theatre is 20°C for a term baby and at least 23°C if a preterm delivery is expected to prevent initial hypothermia.
Preterm infants are at particular risk of hypothermia because of lack of brown fat, small energy reserves, high evaporative heat loss through immature skin and a higher surface area to volume ratio. Sickness places extreme demands on the infant's homeothermic capacity and an unstable core temperature frequently accompanies severe illness. While a healthy term infant can be adequately cared for by dressing and wrapping in warm blankets, sick or preterm infants require incubators or radiant heaters to maintain a normal core temperature.
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Once your pregnancy is over and done with, your baby is happily in your arms, and youre headed back home from the hospital, youll begin to realize that things have only just begun. Over the next few days, weeks, and months, youre going to increasingly notice that your entire life has changed in more ways than you could ever imagine.