Mechanisms of Negative Fetal Outcome in Frontal Vehicle Collisions Involving Unbelted Pregnant Drivers

Abstract

To determine the cause of negative fetal outcomes and the causative mechanism in a frontal collision, we analyzed the kinematics and mechanisms of injuries using an unbelted pregnant dummy, the Maternal Anthropometric Measurement Apparatus dummy, version 2B. Sled tests were performed to recreate frontal impact situations with impact speeds of 13, 26, and 40 km/h. Overall kinematics of the dummy were examined through high-speed video imaging. Quantitative dummy responses—such as time courses of the abdominal pressure, chest deflection, neck injury criteria (Nij), and displacement of the pelvis during impact—were also measured. The maximum abdominal pressure of 103.3 kPa was obtained at an impact speed of 13 km/h. The maximum chest deflection of 38.5 mm and Nij of 0.36 were obtained at an impact speed of 26 km/h. The highest maximum chest deflection of >40.9 mm, Nij of 0.61, and forward pelvis displacement of 478 mm were obtained at an impact speed of 40 km/h. Although the kinematics and mechanism of injuries of the dummy were different for different collision speeds, we found that unbelted pregnant drivers suffer severe or fatal injuries to the fetus even in low-speed collisions.

Factors Affecting the Severity of Placental Abruption in Pregnant Vehicle Drivers: Analysis with a Novel Finite Element Model

“…Therefore, unrestrained pregnant drivers possibly suffer from fatal placental abruption and fetus loss even in collisions at low vehicle speed, when the maternal body slips freely on the driver’s seat to the lower rim of the steering wheel. This result agrees well with the results of previous real-world collision analyses and sled tests using a pregnant dummy model [ 14 , 15 ]. Furthermore, the present results show the risk of suffering placental abruption quantitatively, which has not been reported previously.…”

“…To address this issue, mechanical models (dummy models) specific to pregnant women have been developed for the analysis of collisions involving pregnant women [ 13 , 14 ]. A series of front and rear impact sled tests using anthropometric models of pregnant women have been performed to clarify the mechanisms of injuries in pregnant drivers [ 14 , 15 ]. In frontal impacts, the unrestrained pregnant dummy moved forward, and the dummy’s abdomen directly hit the lower rim of the steering wheel even at a low collision speed of 13 km/h; in rear impacts, a similar phenomenon was observed following a rebound even at a low collision speed of 24 km/h.…”

Severity of Placental Abruption in Restrained Pregnant Vehicle Drivers: Correct Seat Belt Use Confirmed by Finite Element Model Analysis

“…To analyze the placental abruption area with a typical safety equipment setting, we first ran numerical simulations in which we varied the crash speed and lap belt position. For three velocities of 10, 25, and 40 km/h, we accelerated the sled impact test FE model with the waveforms presented in Figure 3 , which were measured in real sled impact tests using a pregnant dummy, MAMA-2B [ 21 , 22 , 23 ]. We ran the simulations for three lap belt positions for the upper, middle, and lower abdomen as illustrated in Figure 4 a–c, respectively.…”