Experimental analysis of the relationship between simulated low-velocity rear-end collisions and fetal outcomes of pregnant rats.

Our study aimed to define the risk for a human fetus of rear-end vehicle collisions. We therefore performed drop tests using pregnant SLC Wistar rats. Pressure applied to the rat uterus and rectum at various stages of acceleration was measured. After being dropped, rats were observed throughout pregnancy. At birth, the numbers, weight and the occurrence of physical anomalies among pups were followed-up for 28 days. Uterine pressure increased exponentially from 2.1 +/- 0.3 kPa at 19-fold gravity (G) to 13.9 +/- 0.8 kPa at 92-fold G. These values are much lower than the mechanical failure level of human fetal membrane tissue or of those at risk of adverse fetal outcomes. Neither the average number of offspring per pregnant rat nor the average body weight of newborn pups differed significantly between control pregnant rats and those which had been exposed to acceleration of 46-fold or 92-fold G. Other variables such as maternal mental distress, motion effects of amniotic fluid or seatbelt-induced uterine injuries might contribute to fetal loss.