In a study led by biomedical engineers at UBC, nearly nine out of 10 pregnant participants failed to achieve the recommended seat belt use, despite instruction and hands-on instruction. Only 11.4% of the 333 participants wore their seatbelts as recommended, suggesting that current seatbelt guidance may be difficult to achieve in practice for many pregnant women.
Seat belts are designed to transfer crash forces directly to the body’s strong skeletal structure. If not positioned correctly, weaker, more vulnerable parts of the body can absorb the force instead, increasing the risk of injury.
Recommended positions are for the shoulder belt to sit between your chest and centered on your shoulders, and for the lap belt to sit under your abdomen and snugly around your hips and pelvis. Most study participants placed the lap belt correctly, but few were able to keep the shoulder belt between their chests. As your pregnancy progresses, your growing belly may cause the shoulder belt to move away from the center of your chest and end up across your chest instead.
Even when the lap belt was placed correctly, nearly one-third of the participants experienced what researchers called “nesting,” where the lap belt folded into the soft tissue beneath the abdomen rather than lying flat against the abdomen. Nesting became more common as pregnancy progressed.
Advances in collision safety research
Researchers say the study highlights broader challenges in vehicle safety research. Human bodies vary widely, and safety models have historically not fully reflected female anatomy, especially during pregnancy.
Pregnancy anatomy poses a different set of challenges to vehicle safety than previously thought, but limited data are available. Our findings suggest an opportunity to study restraint systems to see how new designs can accommodate these changes. ”
Dr. Peter Krypton, Professor, UBC Department of Biomedical Engineering and Principal Investigator
Researchers recruited participants in the maternity clinic at the Jim Pattison Ambulatory Care and Surgery Center in Surrey. Under the supervision of Dr. Jason Burrows, clinical professor of obstetrics and gynecology at UBC, participants were scanned with a handheld 3D imaging tool.
Participants ranged from 6 to 38 weeks of pregnancy and had a variety of body types. The researchers taught them how to wear and adjust their seatbelts and scanned them sitting in production car seats with standard seatbelt configurations.
Reviewing seatbelt design in preparation for pregnancy
Researchers reiterate that safety belts remain the best way to prevent and reduce injuries in car crashes. Research shows that wearing your seat belt correctly can reduce your risk of death in a crash by 47 percent and your risk of serious injury by 52 percent.
“Seat belts save lives and published research supports that seat belts should be worn at all times during pregnancy. The purpose of our study is not to question that guidance, but to help inform how future restraint systems are developed and used,” Dr Krypton said.
This study identified several belt geometry considerations for pregnant occupants that could be further investigated in the future. Lowering the shoulder anchor makes it easier to position the belt between your breasts, but it can also pull the belt away from the center of your shoulders. Raising the anchor improves shoulder position, but may shift it across the chest. With the current seatbelt configuration, many pregnant occupants had difficulty wearing both correctly at the same time.
This research was conducted in collaboration between UBC and the Toyota Collaborative Safety Research Center (CSRC). The team is currently partnering with Autoliv, a maker of restraint systems for Toyota and other automakers, to build computer models of the pregnant anatomy and evaluate future restraint system designs.
“As the automotive industry advances toward virtual testing, opportunities are emerging to include a variety of body sizes, types, and other characteristics in digital human body models for safety research. The data generated in this research will be valuable in informing this development and advancing future occupant protection,” said Dr. Jason Hallman, Toyota Motor Corporation North America Research and Development Division and Toyota CSRC Senior Manager.
The findings will be presented today at the 10th World Congress of Biomechanics in Vancouver.
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University of British Columbia
