The development of sleep-wakefulness cycle and its correlation to other behavior in the human fetus.

Fetal rapid eye movements (REM), breathing movements (BM), and trunk movements (TM) were observed through the use of 3 ultrasonic real-time scanners. Each movement was recorded with the event marker and quantitatively analyzed in relation to the development of the sleep-wakefulness cycle by a computer-assisted system. The results were as follows: The number of REM increased with gestational age. The appearance rate of REM reached a certain level after 32 weeks of gestation. REM-non-REM rhythm was distinguished after 32 weeks. The relationship between REM and BM increased with gestational age. The occurrence of each TM has no correlation to that of REM when it was analyzed in short-term units, but the incidence of TM was high in REM periods. These results demonstrate the course of the development of sleep-wakefulness cycle in human fetuses.