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A finite element model of a seven-month pregnant uterus was created and integrated into a multibody human model. The pregnant occupant model was validated using known abdominal response corridors. Tests of occupants with no restraint, a three-point belt and a three-point belt plus airbag at 35 km/h were simulated to evaluate the effects of four support ligaments connected to the uterus. The primary injury predictor, the peak uterine strain on the anterior uterus, was not found to change appreciably by the absence of the support ligaments; however, high local stress concentrations were found at the ligament attachment sites. Based on these results, it is recommended that computational models of the pregnant occupant contain the supporting ligaments since the stress concentrations may result in increased injury risk in other test configurations or loading conditions.

OBJECTIVE: The goal of this study was to create a computational model of the pregnant occupant of a motor vehicle to predict fetal outcome in crashes. STUDY DESIGN: A finite element uterine model of a 7-month pregnant woman was created and integrated into a multibody human model. Unrestrained, three-point belt, and three-point belt plus airbag tests were simulated at speeds that ranged from 13 to 55 km per hour. RESULTS: Peak uterine strain, as determined by the model, correlated well with the risk of fetal death, as determined by investigations of car crashes. The strain in the uterine wall exceeded the limits of the tissue in simulations of no restraint at 35 km per hour and three-point belt tests at 45 and 55 km per hour. The safest restraint for the pregnant driver is the combination three-point belt and airbag. CONCLUSION: The model is a good first step toward the prediction of the risk of fetal death and verified experimental findings that note the importance of proper restraint use for the pregnant occupant.

The purpose of this paper is to present the crash exposure patterns of pregnant occupants and to evaluate the effectiveness of restraint systems, including four-point seatbelts, in far side crashes. The NASS CDS database revealed that 53.0 % of pregnant occupants are exposed to frontal crashes while 13.5 % are exposed to far side impacts. Given that far side crashes were the second leading crash mode after frontal impacts, a previously validated MADYMO computer model of a 30 week pregnant occupant was utilized to investigate pregnant occupant biomechanics in far side crashes. Three impact speeds (5, 15, and 25 mph) were simulated with four restraint conditions: unbelted, lap-belt only, three-point belt, and a four-point belt. Direct abdominal contact from the shoulder strap of the three-point or four-point belt caused uterine-placental strain in contrast to the inertial loading induced strain in the lap-belt and unbelted cases. Overall, the three-point and four-point belt systems provide superior restraint effectiveness for the pregnant occupant compared to the lap-belt and no restraint cases. The four-point resulted in slightly better performance than the three-point belt by reducing the fetal injury risk and occupant excursion.

Automobile crashes are the largest single cause of death for pregnant women and the leading cause of traumatic fetal injury mortality in the United States. The purpose of this paper is to evaluate the risk of fetal injury in pregnant occupants exposed to far-side vehicle crashes. A test matrix of nine computer simulations was performed using a computational model of a 30-week pregnant occupant. Three separate far-side impact severities were modeled including velocity changes of 5 mph, 15 mph, and 25 mph over the same 100 ms period. Three restraint conditions were modeled including no restraint, lap-belt only, and the three-point belt. All simulations at 5 mph resulted in very low risk of maternal or fetal injury. The simulations at 15 mph and 25 mph demonstrated the protective benefit of the three-point belt as both the lap-belt and no restraint tests resulted in the mother's head contacting the opposite door resulting in severe head injuries with HIC values above 2000. All simulations at 15 mph and 25 mph indicate possible fetal injury risk regardless of restraint condition as the peak strain values at the utero-placental interface were between 27.1% and 44.9% which equate to fetal injury risks between 36.9% and 61.0%. Direct abdominal contact from the shoulder strap of the three-point belt caused this strain in contrast to the inertial loading induced strain in the lap-belt and unbelted cases. Overall, the console was not a potential fetal injury mechanism in these simulations as the occupant either passed over it in the unrestrained simulations or rotated above it for the lap-belt and three-point belt tests. The results of this study are consistent with previous studies that show the three-point belt is the best and most important safety device for protecting pregnant occupants.

A finite element model of a 7-month pregnant uterus was created and integrated into a multi-body human model. The uterine model contains 11,632 elements and 16,335 nodes. The pregnant occupant model was validated using known abdominal response corridors. Unrestrained, 3-pt belt, and 3-pt belt plus airbag tests were simulated at speeds ranging from 13 kph to 55 kph. Peak uterine strain was found to be a good predictor of fetal outcome (R 2 = 0.85). The strain in the uterine wall exceeded 60%, sufficient to cause placental abruption, in simulations of no restraint at 35 kph and 3pt belt tests at 45 kph and 55kph. These tests represent a greater than 75% risk of adverse fetal outcome. For matched tests at 35 kph, strains of 60.8% for the unrestrained occupant, 52.6% strain for the 3-pt seatbelt and only 33.0% strain for the 3-pt seatbelt and airbag combination were recorded. The model proved successful at predicting risk of fetal demise and verified experimental findings noting the importance of proper restraint use for the pregnant occupant.