HMN 2026: How A woman’s birthing position isn’t a choice, it’s a biomechanical strategy

Women’s bodies undergo some of the most intense mechanical demands in human physiology during childbirth and yet the science behind this crucial moment in human life has been largely overlooked for as long as modern science has existed.

A major systematic scoping review led by the University of Lancashire and published in PLOS One has found that not a single study has ever investigated the biomechanics of labor. The review analyzed 87 research papers from around the world, all of which focused solely on pregnancy biomechanics.

None investigated what actually happens to the body during birth and not one of the studies was conducted in the U.K., despite reported rising maternal mortality rates. Ethnicity, a critical factor influencing skeletal structure, mobility and movement patterns, was also entirely absent from the evidence base.

This lack of evidence is not simply academic. Biomechanical factors are known contributors to maternal and neonatal injury and adverse outcomes, yet clinical practice continues to rely on tradition and untested assumptions about laboring bodies.

As a result, labor positions, maneuvers, and techniques used to support labor are often applied without scientific understanding of how they affect the pelvis, spine, soft tissues, or fetal descent, and how these effects may influence maternal and neonatal outcomes.

Dr. Anastasia Topalidou, Associate Professor in Perinatal Biomechanics and Health Technologies, describes this as “a scientific blind spot with real-world consequences for safety and equity in childbirth.

“For marathon running, we’ve mapped every muscle, joint and force involved,” she said. “But when it comes to birth, a far more intense and complex biomechanical event, we tell women to ‘just do it,’ without a single study or any biomechanical evidence to support them.

“We’re delivering babies based on tradition, not science. Labor positions and techniques have never been biomechanically tested, and women and babies are potentially paying the price.”

First experimental step toward filling the gap: Analyzing seven upright birthing positions

To begin addressing this evidence vacuum, researchers from University of Lancashire have conducted the first biomechanical analysis of seven commonly used upright birthing positions, using cutting-edge marker-based and markerless motion-capture systems.

Although this initial study, also published in PLOS One, involved healthy, non-pregnant women in controlled laboratory conditions, it provides the first comparative evidence of how different upright birthing positions affect the pelvis, hips and trunk.

The findings were striking. Each position produced a distinct biomechanical pattern, but even more revealing was how differently individual women assumed the same position. Even in a controlled setting, no two women used the same movement strategy. The data show that one-size-fits-all guidance does not reflect how bodies behave, and that no single “standard” or “optimal” biomechanical pattern exists.

“While clinical guidelines often assume uniformity, the experimental evidence shows that the same position can load the body very differently from one woman to the next,” said Research Associate Dr. Lauren Haworth who worked alongside Dr. Topalidou on the study.

“Labor is one of the most biomechanically demanding processes the human body can undergo. It involves continuous physical and mechanical adjustments, from how the pelvis tilts, to how the trunk balances, to how the body responds to fetal movement.

“This research demonstrates that upright positions align the hips, pelvis, and spine in different ways, meaning they may suit women differently depending on clinical needs, flexibility, balance, comfort, prior injury, or spinal curvature.”

The research team emphasizes that this study is a foundational step, not a clinical recommendation. The next stage is to conduct studies involving diverse pregnant populations, and to develop technologies capable of capturing biomechanical data during real labor in ways that are ethical, unobtrusive, and inclusive.

Dr. Topalidou added, “Until biomechanics is embedded into the education of maternity care professionals, labor support will continue to rely on tradition, assumptions, and guesswork rather than an understanding of how the human body actually functions. Without this knowledge, it will remain difficult to optimize safety, comfort, and outcomes during birth.

“We invest billions to understand rocket trajectories and the mechanics of stars, yet we still cannot describe which movements and techniques best support birth or improve safety and outcomes. This is not a technological limitation; it’s a problem of priorities.”

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