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[Research]Scientists measure how baby bump changes the way women walk, make future safety studies possible

Movie sets are normally the home of three-dimensional motion caption systems, but researchers used the same video recording system in a lab to measure the way pregnant women walk. This is the first research study to use 3D motion capture to create a biomechanical model of pregnant women. The results verify the existence of the “pregnancy waddle” and should enable future studies on how to make everyday tasks safer and more comfortable for pregnant women.

The research team from Hiroshima University studied how pregnant women adjust their movements during daily life, like rising from a chair or changing direction while walking.

Accidental falls cause 10-25 percent of trauma injuries during pregnancy and pregnant women’s risk of falling is the same as women who are 70 years old.

“Biomechanics studies like ours of how humans move are valuable for many things, like making our built environments safer or designing mobility skills,” said Koichi Shinkoda, Ph.D., Professor in the Graduate School of Biomedical and Health Sciences at Hiroshima University.

Previous body scan analysis studies almost exclusively used men of European descent to create mathematical models of the human body. One study in 1996 used pregnant women in Canada, but the imaging technology available at the time has made the data vastly outdated.

“Prior to our study, there were almost no theory-supported models of the movement of pregnant women. This model is just the start of our goal of contributing to a safe and comfortable life before and after childbirth for pregnant women,” said Yasuyo Sunaga, a doctoral student in Shinkoda’s lab and first author of the recent research paper.

The research team brought eight women into the research lab at three different times during their pregnancy, as well as seven non-pregnant women, and used infrared cameras to record their movements using 3D motion capture. After computer analysis of the video, the researchers created virtual models to represent the average pregnant woman.

The model verifies the scientific community’s current understanding of why pregnant women walk differently. Even during the first trimester, pregnant women’s center of mass is farther forward, they lean backwards while standing, and they bend their hips less while walking. This combination can cause a pregnant woman to trip over her toes and more easily lose her balance.

Computer models like this allow researchers to study the limits of what types of movements are safe without putting any research participants in risky situations. The model can simulate potential interventions, saving time and money.

“We want to find the ideal way for new mothers to carry their baby, what exercises are most effective to return to non-pregnant fitness, and what physical postures are best for work in the home or office. Now that we have the appropriate data, we hope to apply our model and make it possible to problem-solve these concerns of daily life,” said Sunaga.

The study will be printed in the July 2016 edition of the journal Applied Ergonomics and is currently available online.

3D Motion Capture of Pregnant Women by Hiroshima University

  • Video CAPTION: Video analysis of women in different stages of pregnancy performing specific movements has been used to create a model that will help researchers make everyday activities safer and more comfortable for pregnant women.
  • Video CREDIT: Research filming by Yasuyo Sunaga, video created by Caitlin E. Devor, both from Hiroshima University.
  • Video LICENSE: Content may only be re-used with attribution.


This study was supported in part by Grants-in-Aid for Scientific Research awarded by the Japan Society for the Promotion of Science (Grant Number 24792502 and 15K11664).

Full Citation

Yasuyo Sunaga, Naohiko Kanemura, Masaya Anan, Makoto Takahashi, Koichi Shinkoda. 2016. Estimation of inertial parameters of the lower trunk in pregnant Japanese women: A longitudinal comparative study and application to motion analysis. Applied Ergonomics: 55, 173-182. DOI:10.1016/j.apergo.2016.02.010.

【Media Contacts】
Yasuyo Sunaga (Assistant Professor, MHSc)
Department of Physical Therapy
Faculty of Health and Social Services
Saitama Prefectural University
sunaga-yasuyo*spu.ac.jp (Please replace * with @)

Norifumi Miyokawa
pr-research*office.hiroshima-u.ac.jp (Please replace * with @)