Neonatal hypothermia and thermoregulation — branching viva

Branch 1 — Why the newborn is vulnerable

Examiner: "Why is this infant cold? Explain the physiology." ^[1]

• The newborn loses heat through four pathways: evaporation (dominant at birth while wet), radiation (skin to cooler walls, the largest in a cold cot), convection (moving air), and conduction (cold surfaces). ^[1]
• The newborn generates heat only by non-shivering thermogenesis in brown adipose tissue — shivering is poorly developed. ^[1]
• The preterm is the extreme: enormous surface-area-to-mass ratio, high transepidermal water loss through immature skin, small brown-fat and glycogen stores (laid down late in the third trimester), and an immature hypothalamus. ^[3]
• Thermogenesis consumes both oxygen and glucose; once glycogen is exhausted, hypoglycaemia deepens and thermogenesis fails — a vicious cycle. ^[9]