DEVELOPMENTAL SEQUENCE OF HUMAN FETAL BODY MOVEMENTS IN THE 2ND HALF OF PREGNANCY

To describe fetal body movements precisely and to clarify their develo pmental sequence in the second half of pregnancy, fetal body movements were observed in 31 normal fetuses between 20 and 41 weeks of pregnan cy by using multiple ultrasonic machines. All movements of the whole t runk were able to be classified into six fundamental movements: flexio n, stretch, rolling, startle, stepping, and writhing. Startle was alwa ys observed as a single movement, but others were more frequently obse rved as a part of combination rather than as a single movements. The i ncidence of flexion and stretch peaked at 28-31 weeks, whereas the inc idence of startle and stepping lowered at the period. The incidence of rolling and upper half trunk movements increased at 40-41 weeks. Limb movements were frequent and did not exhibit characteristic change in the incidence. In conclusion, we classified fetal body movements into several fundamental movements instead of using the expression of ''gen eral movements'' by focusing principally on movements of the trunk. In particular, some of the fundamental movements seem to appear in chara cteristic ways as related to gestational age. In view of that fetal be haviors are closely related to the neural activity, the present findin gs may contribute to an understanding of the developmental process of the central nervous system.