To examine the effect of seatbelt using for pregnant women drivers, sled tests were performed. Changes of intra-uterine pressures in anthropometric dummies representing pregnant women were examined. At the low speed of frontal collision, seatbelt reduced the forward movement of the dummy and subsequently decreased peak intra-uterine pressure by 55% to 65%. At rear-end collision with 6.5 G of acceleration, seatbelt also reduced the forward movement of the dummy due to rebound and prevented the second impact between steering-wheel and the abdomen. This traumatomechanical study using pregnant dummy with varying impact dynamics is useful for improving the seatbelt use in pregnant women drivers.