How does a newborn most commonly lose heat immediately after birth?

A newborn most commonly loses heat immediately after birth through evaporation. After delivery, the baby is exposed to the cooler environment outside the womb, and any moisture on their skin, particularly amniotic fluid, begins to evaporate. This process of evaporation requires heat, which is drawn from the baby's body, leading to a significant loss of temperature.

Evaporative heat loss is particularly critical in the first moments following birth because newborns have a relatively high surface area-to-volume ratio and limited ability to generate heat. Before they are dried off or wrapped, the moisture on their skin contributes to cooling.

Understanding the mechanism of heat loss is essential in neonatal care, as maintaining normothermia is paramount to prevent hypothermia complications. Immediate interventions often include drying the infant thoroughly and providing skin-to-skin contact to prevent further heat loss.