Nocturnal sleep organization during the first months of life.

42 healthy infants (18 boys and 24 girls) aged 4-30 weeks had polygraphic whole night recordings. Four sleep stages were identified, using standard sleep scoring parameters: intervening wakefulness (W), quiet sleep (QS), active sleep (AS) and transitional sleep (TS). Our results show, first, an important decrease of the intervening wakefulness between 4-5 weeks and 6-7 weeks, then a modification of the distribution of this intervening wakefulness after 21-22 weeks. QS increases significantly from 4-5 weeks to 27-30 weeks with a linear distribution throughout the night. The QS modifications seem related to the appearance of sleep spindles between 6 and 11 weeks. Intervening wakefulness and quiet sleep changes appear simultaneously with the emergence of the circadian rhythm. Active sleep and transitional sleep remain stable from 4-5 weeks to 30 weeks. Furthermore, no change in the internal organization is observed for active sleep during this period.