Children under 4 years of age fare better in motor vehicle accidents when they are riding in rear-facing rather than forward-facing car seats, according to a report published online in the British Medical Journal.

Infants are typically switched from a rear- to a forward-facing seat when they reach about 20 pounds, which occurs at roughly 8 months of age for an average boy, study authors Dr. Elizabeth A. Watson and Dr. Michael J. Monteiro, from Royal Surrey County Hospital, Guildford, U.K., note. They add, however, that growing evidence suggests it may be best to delay the switch until 4 years of age.

For example, there are data that many fatalities in young forward-facing riders could have been averted with a rear-facing seat. An analysis of U.S. National Highway Traffic Safety Administration data of 870 children involved in crashes from 1998 to 2003 found that through 23 months of age, better protection from all crash types was provided with rear-facing seats.

In terms of specific injuries, recent crash test results suggest that rear- rather than forward-facing seats provide better protection of the lower neck and chest, the authors note. In another crash simulation study, it was concluded that manufacturers should developed rear-facing seats for children up to 4 years old.

Watson and Monteiro note that in contrast to forward-facing seats, rear-facing seats provide full alignment of the head, neck, and spine, so that crash forces are dispersed over these areas rather than centered on one site.

The message for healthcare professionals, the authors say, is that they should recommend rear-facing car seats for children under 4 years of age. To fully address the issue, however, seat manufacturers and retailers need to "increase the availability of rear-facing car seats for children over 20 pounds."