Sleep ontogenesis in early human prematurity from 24 to 27 weeks of conceptional age

The spontaneous behavior of 5 previable human prematures born between 24 and 27 weeks of gestational age and weighing between 600 and 900 g was studied, between the 3rd and 30th hr of life. Death occurred between the 28th and 120th hr. Body motility, eye movements, respiratory and cardiac rhythms, chin myogram, electroencephalogram (EEG), and crying were evaluated by careful observation and by polygraphic recordings for periods of from 1 to 2 hr. A very rich and continuous motility is described consisting of rapid jerks, either diffuse or localized, and of slow movements. Rhythmic movements of the chin or peribuccal area occur in bursts and are particularly striking. The paucity of rapid eye movements (REM) is also remarkable. The EEG is composed of silent periods interrupted by discontinuous polymorphic activity. The fixation of the cardiac rate, the absence of periodic respiration and of apneic periods are the most important vegetative phenomena. Crying occurs in short periods rarely lasting more than 20 sec. The state of these previable prematures cannot be considered as waking; it seems to be a very immature state of sleep that differs from both the quiet and the active sleep of full‐term newborns. This atypical sleep, which appears to be present in other species characterized by a great degree of immaturity at birth, does not give any evidence of cyclic organization.