The Effect of Pregnant Occupant Position and Belt Placement on the Risk of Fetal Injury

The goal of this project was to evaluate the effect of occupant seating and seatbelt placement on the risk of adverse fetal outcome from a motor vehicle crash. Unrestrained, 3-pt belt, and 3-pt belt plus airbag tests were simulated with the Virginia Tech pregnant occupant computational model in both a driver-side and passenger-side vehicle interior in frontal impacts at 35 kph. The pregnant occupant model is a small female human body model modified to include a finite element uterine model. The model was previously created and validated with abdominal force-deflection responses. Peak uterine strain was reduced by 30% to 50% in passenger-side simulations vs. driver-side simulations. However, in the unrestrained, passenger-side simulation, the pregnant occupant sustained a HIC score of 2820, suggesting immediate maternal death and a high likelihood of fetal death. Additional simulations were run in which the vertical position of the lap-belt was varied through three heights. It was found that the vertical position of the lap-belt can increase the risk of adverse fetal outcome by a factor of three. The worse case lap-belt height corresponds to the belt being placed directly over the placenta. This case produced a peak uterine strain of 97%, well above the reputed tissue limit of 60%. It is recommended that, when practical, the pregnant woman ride in the passenger seat with a 3-pt belt. The seat should be positioned as far rearward as possible and the lap-belt should be worn as low as possible