Nearly nine in 10 pregnant participants in a study led by biomedical engineers at UBC did not achieve recommended seatbelt placement, even after instruction and hands-on guidance. Among 333 participants, only 11.4 per cent were able to place the seatbelt as recommended, suggesting current seatbelt guidance may be difficult for many pregnant people to achieve in practice.
Seatbelts are designed to direct crash forces through the body’s sturdy skeletal structure. When they’re not positioned correctly, the body’s weaker, more vulnerable parts may absorb those forces instead, increasing the risk of injury.
Recommended positioning places the shoulder belt between the breasts and centred on the shoulder, while the lap belt sits below the abdomen, fitting snugly across the hips and pelvis. Most study participants positioned the lap belt correctly, but few managed to keep the shoulder belt between the breasts. As pregnancy progresses, abdominal growth can push the shoulder belt off the centre of the chest and across the breast instead.
Even when the lap belt was positioned correctly, nearly one-third of participants experienced what researchers called “nesting,” where the lap belt folded into soft tissue beneath the abdomen instead of lying flat against it. Nesting became more common as pregnancy progressed.
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, particularly pregnant anatomy.
“Pregnant anatomy introduces a different set of challenges to motor vehicle safety than has previously been considered, yet there is limited data available,” said Dr. Peter Cripton, a professor in UBC’s school of biomedical engineering and the study’s lead researcher. “Our findings suggest an opportunity to study restraint systems to see how new designs could accommodate these changes.”
The researchers recruited participants at the maternity clinic of the Jim Pattison Outpatient Care and Surgery Centre in Surrey. Under the supervision of UBC obstetrics and gynecology clinical professor Dr. Jason Burrows, participants were scanned with handheld 3D imaging tools.
Participants ranged from six to 38 weeks pregnant and represented a broad range of body types. Researchers showed them how to wear and adjust a seatbelt, then scanned them seated in a production vehicle seat with a standard seatbelt configuration.
The researchers reiterate that safety belts are still the best way to prevent and reduce injuries in a car crash: seatbelts worn correctly can reduce the risk of death in a collision by 47 per cent and the risk of serious injury by 52 per cent, according to research .
“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,” said Dr. Cripton.
The study identified several belt geometry considerations for pregnant occupants that can be further studied. Lowering the shoulder anchor helps position the belt between the breasts but can pull it away from the centre of the shoulder. Raising the anchor improves shoulder placement but can move it across the breast. With current seatbelt configurations, many pregnant occupants struggled to get both right at the same time.
The study was a collaboration between UBC and the Toyota Collaborative Safety Research Center (CSRC). The team is now partnering with Autoliv, a manufacturer of restraint systems for Toyota and other automakers, to build computer models of pregnant anatomy and evaluate future restraint system designs.
“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,” said Dr. Jason Hallman of Toyota Motor North America Research and Development and senior manager for the Toyota CSRC.
The findings will be presented today at the 10th World Congress of Biomechanics in Vancouver.
Interview language(s): English
Observational study
People