A Finite Element Model of the Pregnant Female Occupant: Analysis of Injury Mechanisms and Restraint Systems

For women of reproductive age, automobile crashes are the leading cause of death worldwide. It has been estimated that 40,000 women in the second half of pregnancy are involved in motor-vehicle crashes each year. It has been estimated that between 300 to 3800 will experience a fetal loss. Placental abruption has been shown to account for 50% to 70% of fetal losses in motor vehicle crashes. While there is a growing database of medical case studies and retrospective studies describing the outcome of motor vehicle accidents involving pregnant occupants, as well as the effect of seatbelts on fetal survival, previous research has not produced a tool for engineers to use to improve the safety of a pregnant occupant in a motor vehicle. The goal of this project was to develop a model that can quantify the stresses and strains on the uterus of a pregnant woman in order to predict the risk of injury. A finite element uterine model of a 7-month pregnant female was created and integrated into a multi-body human model. 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. The uterine strain sufficient to cause placental abruption was seen in simulations known to have greater than 75% risk of adverse fetal outcome. Head injury criteria (HIC) and viscous criterion (V*C) were examined as a check of overall occupant protection. The 3-pt belt plus airbag restraint provided the greatest amount of protection to the mother.

The model proved successful at predicting risk of fetal demise from placental abruption and verified experimental findings noting the importance of proper restraint use for the pregnant occupant.