Unborn babies have missed out on the trend for passenger safety systems - until now. William Wadsworth reports
THESE DAYS, everyone in a car is protected by comprehensive safety systems. Everyone, that is, except an unborn child, because automotive researchers still know surprisingly little about foetuses in car accidents. In its effort to shed more light on the matter, Volvo Car Corporation has developed the world's first official computer model of a pregnant crash dummy.
Camilla Palmertz, a biomechanical engineer at the Volvo Cars Safety Centre, in Gothenburg, Sweden, says: 'This virtual crash dummy is a woman at a late stage of her pregnancy, since that is when the unborn baby is at greatest risk in an accident. The basic geometry was completed by January. Since then much time has been devoted to refining the model. Now it's finished and we've started running simulated front-end impact tests on it.'
The purpose of the study is to see how the virtual mother-to-be and her unborn baby are affected by the seat-belt and airbag in simulated accidents, Palmertz says. 'The computer model makes it possible to study - in great detail - how the belt moves, the influence of belt and airbag on the uterus, placenta and foetus, and how the foetus moves in relation to the mother's body. Among other things. The model can also be used to test new designs for seat-belts and other safety systems.'
Many pregnant women wonder whether the seat-belt could harm their unborn baby if they were involved in an accident. Researchers all recommend that they should always wear the safety device. But it's important to wear it in the right way, Volvo's researchers say, adding the belt should be between the breasts and as low as possible over the hips. 'The lap section of the belt mustn't be allowed to ride up in front of the woman's tummy,' says Palmertz. 'That could harm the baby.'
In an accident, the pregnant passenger's thorax and pelvis are both restrained by the belt, but her abdomen is free to move in the direction determined by the particular forces arising from the impact. Because the baby is floating free inside the mother, the unborn child's injuries tend to fall into two main types. The more common is that the placenta becomes either partially or completely detached, which means the baby cannot get enough oxygen. The rarer scenario is for the head of the baby to be injured if it hits one of the bones of the mother's pelvis.
'We think that the placenta may become detached because, while the uterus is relatively elastic and can therefore change shape, the placenta is not equally resilient under acceleration,' Palmertz explains. 'We don't know yet. That's why this model is so important.'
Meanwhile, recent biomechanics research at the University of Halmstad, in Sweden, reveals that although all the country's women belt up when they are pregnant, they are not told exactly where to 'clunk-click' for the best protection of their baby.
The researchers gathered initial data from 139 pregnant women and new mothers, which was followed up with interviews. All but one said they had always used a seat-belt before pregnancy. Several women in the final stages of pregnancy said that they were now using seat-belts less. The reasons they gave were that the belt chafed, that they were afraid the baby might be affected, and that it was difficult to put on. Almost half of the women in the late stages had experienced problems with the belt moving upwards onto the tummy instead of remaining across the hips.
In a similar study in the United States, the majority of the sample of 200 said wearing a seat-belt was uncomfortable, that it chafed and that it slipped upwards onto their tummies.
Many of them also stopped using seat-belts while pregnant. These differences could well be a question of habit. In Sweden, wearing seat-belts in the front seats became compulsory in 1975. The equivalent American laws are rather more recent.