When Dr. Peter Cripton and his team at the University of British Columbia started scanning pregnant bodies with 3D imaging tools, they expected to find some challenges with seatbelt fit. What they discovered was striking: out of 333 pregnant participants, only 11.4% could position their seatbelt exactly as safety guidelines recommend — even after receiving hands-on instruction.
The study, published by UBC's School of Biomedical Engineering, used handheld 3D scanners to map how pregnancy changes the way seatbelts sit on the body. Participants ranged from 6 to 38 weeks pregnant and were recruited at the Jim Pattison Outpatient Care and Surgery Centre in Surrey, British Columbia. Each person was shown how to properly wear a seatbelt, then scanned while sitting in a real car seat with a standard belt configuration.
The researchers found that most pregnant people could place the lap belt correctly — below the abdomen, across the hips. But the shoulder belt was another story. As the abdomen grows, it pushes the shoulder belt away from its recommended position between the breasts and toward the center of the chest. "Pregnant anatomy introduces a different set of challenges to motor vehicle safety than has previously been considered," said Dr. Cripton, the study's lead researcher.
Another surprising finding: even when the lap belt appeared to be positioned correctly, nearly one-third of participants experienced what the researchers called "nesting" — the belt folded into soft tissue instead of lying flat against the body. This problem became more common as pregnancy progressed.
Here is the important part, though: the researchers are not suggesting pregnant people skip their seatbelt. Studies show that properly worn seatbelts reduce the risk of death in a crash by 47% and serious injury by 52%. "Seat belts save lives, and published studies support that they should always be worn during pregnancy," Dr. Cripton said. "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 is already putting their findings to work. They have partnered with Autoliv, a company that makes seatbelts and airbags for Toyota and other automakers, to build computer models of pregnant anatomy. The goal is to design restraint systems that fit pregnant bodies as well as they fit everyone else.
This matters because car safety research has historically used body models that do not fully reflect female anatomy, especially during pregnancy. By creating better data, Dr. Cripton and his colleagues hope to push the automotive industry toward designs that protect everyone on the road — no matter how their body changes.
The study was a collaboration between UBC and the Toyota Collaborative Safety Research Center.