Activity patterns assessed throughout 24-hour recordings in preterm and near term infants.

The motility of 10 low-risk infants, aged between 34 and 40 weeks of postmenstrual age, has been continuously recorded for 24 h. Four codes were distinguished: code 1 (absence of motility or occasional occurrence of startles), code 2 (presence of small general or isolated body movements, startles, smiles, grimaces, and other facial activity), code 3 (forceful and prolonged general movements, startles, and stretches), code 4 (vigorous and abrupt general body movements accompanied by crying). Changes with age concern mainly the increase of the duration of code 1 (quiescence) episodes. Confrontation between day and night showed higher levels of motility during the night than during the day. The last weeks before term represent a time for increase in the ability to sustain a quiet behavior and to reorganize day-night motility distribution.