[Developmental sequence of fetal behavior and the functional development of the fetal central nervous system]

The development of central nervous system (CNS) is the latest among the various fetal organs and is on the way to mature even at birth. Because behavior is the phenotype of the CNS function, the behavioral pattern significantly changes with the developmental stage of CNS throughout the whole fetal period. The purpose of this study is to clarify the developmental sequence of fetal behavior and to discuss the functional development of the fetal CNS. For the first step of this study, thirty-one normal pregnant women, between 20 and 41 weeks of gestation, were examined for 60 minutes by using four ultrasonographic machines, which were employed simultaneously for observing four parts of each fetus: head, trunk, upper and lower extremities. All fetal movements were categorized according to the moving parts of the body and the peculiarities of movement. Trunk movements include six types i.e. flexion, stretch, rolling, startle, jumping (stepping), and writhing. The peak incidences of flexion and stretch were in 28-31 weeks of gestation. The incidence of rolling movements was high in 24-27 weeks, thereafter lowered gradually with gestational age, and then showed the significant increase in 40-41 weeks. The incidences of startle and jumping movements were high before 28 weeks, and then decreased significantly. Writhing movements were often observed after 28 weeks. The other movements showed the respective patterns of the changes in the incidence. Secondly, animal experiments were performed to obtain the basic data on fetal behavior which could not be given by the ultrasonographic observation of human fetuses. Fetal goats were incubated under the physiological condition in artificial amniotic fluid by using extracorporeal membrane oxygenation (ECMO) system.(ABSTRACT TRUNCATED AT 250 WORDS)