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Updated: Feb 15, 2026

Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
Species-specific Posture of Human Foetus in Late First Trimester
Yoshiyuki Ohmura1, Seiichi Morokuma2,3, Kiyoko Kato3
1Department of Mechano-Informatics, Graduate School of Information Science and Technology, The University of Tokyo 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan. ohmura@isi.imi.i.u-tokyo.ac.jp.
Abstract:
The ontogeny associated with the arm-hanging posture, which is considered ape-specific, remains unknown. To examine its ontogeny, we measured foetal movements of 62 human foetuses aged 10-20 gestation weeks using four-dimensional sonography. We observed that the first-trimester foetuses show this particular species-specific posture. After 11 weeks of gestation, all foetuses showed the arm-hanging posture, and the posture was most frequently observed at 14-16 weeks of gestation. Moreover, this posture often involved extension of both arms and both legs, indicating that it is not myogenic but neurogenic. Furthermore, early ontogeny suggests that it originates because of subcortical activity. Such posture extension bias and persistence indicates that vestibulospinal tract maturation involves the ontogeny of arm-hanging posture during 14-16 weeks of gestation.
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