Nine premature and 28 full-term infants were observed in their homes for 7 hr when they were 2, 3, 4, and 5 weeks post-term, and the sleeping and waking states displayed by these infants were compared. For these comparisons, the observation day was divided into two mutually exclusive contexts: times when the baby was alone and times when the baby was with the mother. The premature infants spent more time alone (mean of 5.4 hr a day) than the full-terms (4.6 hr).

Over the total 7-hr day, the premature infants spent more time in alert, nonalert waking activity, and sleep-wake transition than the full-terms, and they spent less time in drowse and total sleep. These results clearly indicate that, at the same post-term ages, the sleep-wake states of premature infants differ markedly from those of full-terms. Four states showed significant Group × Context interactions indicating that state differences between premature and full-term infants were also a function of the context in which the infants were observed. For example, the prematures exhibited more fuss or cry and more drowse when alone; whereas the full-terms exhibited more of these states when with their mothers. This finding of context-related differences between prematures and full-terms has implications for the conflicting reports in the literature, as heretofore the states of prematures and full-terms have been compared from observations made in a single situation.

The results indicate that prematures exhibit significant commonality in their neurobehavioral development through the early post-term period despite heterogeneity among them in their exposure to prenatal, perinatal, and early postnatal stresses.