Evaporative heat loss predominates during skin maturation in extremely preterm infants

This prospective observational study followed 30 infants born at 22–28 weeks’ gestation in a tertiary neonatal intensive care unit. Investigators measured transepidermal water loss, insensible water loss from the skin and heat-loss components from postnatal day 1 to day 28. Mixed-effects models assessed changes over time and differences among four gestational-age groups, accounting for incubator temperature and humidity.

Insensible water loss from the skin differed across gestational-age groups (overall p<0.001) and was higher in the 22–23-week and 24–25-week groups than in infants born at 28 weeks. Both insensible water loss and transepidermal water loss declined nonlinearly over postnatal time, with faster early decreases followed by stabilization. Evaporative heat loss consistently made up the majority of total heat loss across all gestational-age groups.

The findings characterize early skin-barrier maturation and heat loss in this population, but do not test whether an intervention to control evaporation improves clinical outcomes. Environmental associations may reflect protocol-driven incubator management rather than independent physiological effects. The small, single-unit observational study also excluded infants who died before longitudinal measurements could be completed; all infants in the final analysis survived to discharge.