Water loss from the skin of term and preterm babies.

Water loss from the skin of term and preterm babies, nursed naked in incubators under neutral thermal conditions, was measured by a method based on estimating the water vapour pressure gradient close to the skin surface. 199 sets of measurements were made on 78 babies whose gestational ages ranged from 26 to 41 weeks, during the first 4 weeks of life. Babies of 34 to 41 weeks' gestation had high water losses in the first 4 hours after birth, which then fell to low levels averaging 6 g/m2 per hour. Babies of 30 to 33 weeks' gestation had high water losses in the first week which then fell to levels similar to those of mature babies. Babies less than 30 weeks' gestation had strikingly high losses, averaging 32 g/m2 per hour in the first 4 days of life. At 2 weeks, levels were still higher than those of mature babies. Light-for-dates babies had skin water losses appropriate for their gestations. The high water losses in extremely preterm babies are probably transepidermal and the result of a thin, poorly keratinised stratum corneum. Water loss from the palms and soles was high in term babies and although low in preterm babies it rose steadily in the first 4 weeks of life. This is thought to represent the onset of emotional sweating. In terms of actual heat and water lost, skin water loss is relatively unimportant in term babies nursed naked under neutral thermal conditions. However, in babies less than 30 weeks' gestation, weighing less than 1 kg, skin water loss makes a major contribution to overall water balance. Furthermore, evaporative heat loss from the skin may exceed resting heat production. It is suggested that reduction of skin water loss in these babies may increase their chances of survival and their rates of growth.