Final answer:
Newborns lose heat rapidly due to a higher ratio of surface area to volume, immature musculature, underdeveloped nervous systems, and little subcutaneous fat for insulation.
Step-by-step explanation:
Newborns lose heat rapidly due to several factors. Firstly, they have a higher ratio of surface area to volume than adults, which means they have more surface area from which to lose heat. Additionally, newborns have immature musculature and underdeveloped nervous systems, limiting their ability to generate heat by shivering and to constrict blood vessels in response to cold. They also have little subcutaneous fat for insulation. Lastly, newborns produce heat more slowly, making it harder for them to maintain their body temperature.