A child's neck is under development and not as strong as an adult's neck. Also the head is proportionally bigger than that of an adult. Children therefore need special restraints, facing the rear for as long as possible until at least three-four years of age. When travelling facing the rear the crash forces are spread over the back and head, which reduces the load on the neck in frontal impacts.
If a pregnant woman uses her safety belt correctly, the foetal injury risk is reduced significantly. This knowledge stems from Volvo Cars' research on car safety for unborn babies and their mothers. Volvo Cars has developed a virtual crash test dummy to simulate frontal impacts during pregnancy.