Shorter pregnant women restrained in the rear seat of a car are at risk for serious neck injuries: Biomechanical analysis using a pregnant crash test dummy.

INTRODUCTION: When considering seat belt contacts to the neck in pregnant woman of shorter height sitting in the rear seat of a vehicle, subsequent injuries after a collision must be understood in the context of both maternal and fetal outcomes. To determine likely injuries to a pregnant woman sitting in the rear seat, we determined the kinematics of a "pregnant" crash test dummy by measuring neck compression forces and biomechanical parameters acting on the head and neck. METHODS: Sled tests using a shorter-height pregnant woman crash test dummy (Maternal Anthropometric Measurement Apparatus, ver. 2B) were performed at the HYGE sled test facility representing full frontal impact at target velocities of 29km/h and 48km/h. Kinematics of the dummy and biomechanical parameters of the head, neck, and chest were measured. Pressure to the neck was measured using Prescale (Fujifilm, Tokyo, Japan). RESULTS: During frontal collision tests, the shoulder belt compressed the neck at a pressure >12.8MPa, even during the low-velocity impact. In addition to neck flexion, right side bending and the head and chest moving in opposite directions were observed, with maximum differences of 42.4mm at high velocity and 33.7mm at low velocity. CONCLUSIONS: This study provides data on the kinematics of pregnant women of short height sitting in the rear seat during a frontal collision using a pregnant woman crash test dummy. The knowledge gathered from this study should be useful for determining pregnant women passengers' kinematics at the time of collision and evaluating the relationship between the vehicle collision and fetal outcomes.

Seatbelt paths of the pregnant women sitting in the rear seat of a motor vehicle.

PURPOSE: Seatbelt use during pregnancy is important to improve maternal and fetal survival after motor vehicle collisions. However, because the rear seatbelt of a motor vehicle tends to make contact with the neck, even if it is adequately used, some pregnant women sitting in the rear seat opt not to fasten the belt. The purpose of this study is to explore seatbelt-neck contact for pregnant women sitting in the rear seat of a motor vehicle. METHODS: We carried out an anthropometric study. Japanese women who were ≥30 weeks pregnant (n = 12) sat in the left side of the rear seat of a typical mid-size passenger sedan and fastened the seatbelt. Seating posture was investigated by measuring the coordinates of the anthropometric data points of the pregnant women (head, shoulder, hip joint, and knee joint). The belt path was analyzed by measuring the clearance between the belt and the sternum or navel. RESULTS: Among the 12 pregnant women at 33.9 week ± 3.3 week gestation, the shoulder belt deviated to the right side and subsequently contacted to the neck in four pregnant women (Contact group). The height of the Contact group was significantly shorter than that of Non-contact group (152.3 cm ± 3.0 cm vs. 159.0 cm ± 3.3 cm, p = 0.008). Regarding the relative position of the seatbelt to the subject's body, the distances from the top of the sternum to the center of the shoulder belt were significantly shorter in Contact group (3.9 cm ± 3.5 cm) than that in the Non-contact group (8.0 cm ± 1.6 cm, p = 0.03). However, no significant difference was found for the distance from the umbilicus to the center of the lap belt. CONCLUSION: Our findings show that because of short height and late term of pregnancy with protrusion of the abdomen, the shoulder belt deviates to the right or left, avoiding the protruded uterus, and subsequently makes contact with the neck. Seatbelt systems for rear seats need to be developed to improve passenger safety, especially for pregnant women.