Yawning and behavioural states in premature infants.

Low risk, premature infants between 30 to 35 weeks post-conceptual age (PCA) residing in an neonatal intensive care unit environment were observed in the home incubator for spontaneous yawning from 2400 to 0500 hr. Videorecordings were analyzed for the behavioral states of quiet sleep (QS), active sleep (AS), wake (W), and drowse (D) in 3-min epochs as well as the contextual behaviors before and after yawn events using a 1-min window. Yawning periods predicted higher levels of motoric activation than nonyawn periods. Sequence analysis of preceding and following states with or without yawns were examined for stability or change. All states with or without yawn events had state stability for the preceding and following epochs, with two exceptions: 1) D state with yawning was associated with state change in the preceding 3-min epoch (most often W), and 2) D state without yawning was associated with state change in the following epoch (W or AS). Yawns were not present in QS. The results suggest that yawning is associated with increased behavioral arousal that is not state-specific. However, yawning in D state predicts state transitions in the preceding, but not the following, epoch. It is proposed that D may be an unstable state that becomes more stable when yawning is present.