Sweating in preterm babies.

The development of thermal sweating was investigated in 117 studies on 85 term and preterm infants. The babies were nursed naked in an incubator and exposed to progressively higher air temperatures until sweating occurred or until the rectal temperature reached 37.9 degrees C. Most babies of 36 weeks' gestation or more were able to sweat from the first day. Babies of less than 36 weeks' gestation did not sweat initially. However, postnatal existence hastened the development of sweating so that by 13 days all babies studied were able to sweat. Sweating occurred first and was most marked on the forehead. The intensity and extent of the sweat response depended on gestational age. With postnatal age the extent of the response rapidly increased but the intensity only rose slowly. The air temperature required to induce sweating was higher in the more immature babies but fell with postnatal ge. Although even the most immature infant soon develops the ability to sweat in response to heat stress, the efficiency of sweating as a thermoregulatory process is poor.