Newborn Thermoregulation

Thermoregulation can be defined as the set of physiological processes that maintain body temperature within a precise range by balancing heat production and loss.
At birth, the newborn must face a significant thermal shift, coming into contact with an environmental temperature that is considerably lower than the intrauterine one (which is about 0.3–0.5°C higher than the mother’s body temperature). As a result, the newborn must learn to produce heat to counteract the cooling effect of this new condition. Generally, a full-term healthy newborn is able to regulate their body temperature by producing enough heat to compensate for the sudden drop. Supported by skin-to-skin contact with the mother and subsequently warmed by her hugs and cuddles, the baby begins to learn thermoregulation within a few hours.

In newborns, the ability to generate heat through shivering thermogenesis is limited due to the immaturity of the muscular system and neuroendocrine control. Consequently, the main mechanism for heat production is non-shivering thermogenesis (NST), mediated by brown adipose tissue, which is particularly abundant in newborns.

Heat production mainly occurs thanks to a system of thermoreceptors connected to the central nervous system. When the perceived temperature drops below the normal range, peripheral vasoconstriction is activated to reduce heat loss, and sweating is inhibited. Heat dissipation, on the other hand, occurs naturally, mainly through peripheral vasodilation and, to a lesser extent, through evaporation via sweating.

Thermoregulation is orchestrated by a complex system consisting of:

• Peripheral thermoreceptors, located at the skin level (e.g., Krause’s end bulbs for cold and Ruffini endings for heat), which detect environmental temperature changes and send afferent sensory signals;
• Central thermoreceptors, located in the hypothalamus, spinal cord, and visceral organs, responsible for detecting blood temperature with sensitivity to variations as small as 0.1°C;
• Hypothalamic integration system, which processes information from both peripheral and central sources and triggers efferent responses aimed at maintaining body temperature within physiological limits.

Finally, it should be noted that under normal conditions, a newborn’s body temperature is slightly higher than that of an adult, and issues such as colic or teething may cause a temporary increase in temperature.