ABSTRACT
The presence of behavioral states has been recognized in human fetuses. However, developmental
process of fetal behavioral states remains to be clarified. In thirty-one normal pregnant
women between 20 and 41 weeks' gestation, fetal movements were examined by using multiple
ultrasonic machines. The entire period was divided into eye movement (EM), no eye
movement (NEM), and unclassified periods according to the mode of appearance of rapid
eye movements. We investigated changes in the ratio of EM and NEM periods and the
incidence of various fetal movements in these periods. The ratio of EM periods increased
stepwise between 20 and 32 weeks. The difference in the incidence of “startle” and
jaw movements between EM and NEM periods was found at 24-27 and 32-35 weeks, respectively.
We found a significant decrease in the incidence of total body movements exclusively
in NEM periods at 36-39 weeks and a significant increase in the incidence of “rolling”
in EM periods at 40-41 weeks. Eye opening was ultrasonographically recognized, providing
evidence for awake state in the human fetus. This study revealed the characteristic
appearance of fetal movements as related to the presence or absence of EM during the
second half of pregnancy, and thereby pointed to differential development process
of behavioral states of human fetuses.
Keywords
fetus - fetal movements - behavioral states - ultrasound
