In newborns, the majority of insensible water loss is via which route?

• A. Respiratory tract
• B. Gastrointestinal tract
• C. Skin and respiratory tract contribute equally
• D. Skin

Answer: (D)

The main idea is that newborns lose most of their insensible water through the skin. Their skin has a large surface area relative to body weight and an immature, thin barrier that permits rapid evaporation, so evaporative water loss via the skin is substantial. In comparison, water loss through the respiratory tract is smaller, and the GI tract doesn’t contribute to insensible losses in the same way (stool and urine are sensible losses). Therefore, skin is the dominant route of insensible water loss in neonates, especially in preterm infants whose skin is even more permeable.