Nearly nine in 10 pregnant participants in a study led by biomedical engineers at the University of British Columbia did not achieve recommended seatbelt placement, even after instruction and hands-on guidance, according to findings released on July 14. Among 333 participants, only 11.4 percent were able to place the seatbelt as recommended, raising concerns that current seatbelt guidance may be difficult for many pregnant people to follow in practice.
Seatbelts are designed to direct crash forces through the body's sturdy skeletal structure. When they are not positioned correctly, more vulnerable parts of the body may absorb those forces instead, increasing the risk of injury. Recommended positioning places the shoulder belt between the breasts and centered on the shoulder, while the lap belt sits below the abdomen and fits snugly across the hips and pelvis.
The study found that most participants positioned their lap belts correctly but few managed to keep their shoulder belts between their breasts. As pregnancy progresses, abdominal growth can push the shoulder belt off center and across one breast instead. Even when lap belts were positioned correctly, nearly one-third of participants experienced what researchers called "nesting," where the lap belt folded into soft tissue beneath the abdomen rather than lying flat against it—a trend that increased with pregnancy progression.
Researchers said these findings highlight broader challenges in vehicle safety research due to variations in human anatomy. Safety models have historically not fully reflected female anatomy or accounted for changes during pregnancy.
The study was conducted at Jim Pattison Outpatient Care and Surgery Centre's maternity clinic in Surrey under supervision from Dr. Jason Burrows. Participants ranged from six to 38 weeks pregnant with diverse body types; they received demonstrations on proper seatbelt use before being scanned seated in a production vehicle seat using handheld 3D imaging tools.
Dr. Cripton said, "Seatbelts save lives and published studies support that they should always be worn during pregnancy. The goal of our research is not to question that guidance, but to help inform how future restraint systems are developed and used." The team identified several considerations for improving restraint systems for pregnant occupants related to anchor position adjustments but noted current configurations make achieving both correct placements challenging.
The project was a collaboration between UBC and Toyota Collaborative Safety Research Center (CSRC). Researchers are now working with Autoliv—manufacturer of restraint systems—to build computer models representing pregnant anatomy for evaluating new designs. Dr. Jason Hallman of Toyota Motor North America Research and Development said, "As the automotive industry progresses toward virtual testing, there is an opportunity to include varying body sizes, types and other properties in digital human body models for safety research. The data generated by this study is valuable for informing this development and advancing future occupant protection." The findings will be presented at Vancouver's 10th World Congress of Biomechanics.
