Parents should be advised to keep their children in rear-facing car seats until at least the age of four, conclude authors of a new British study.

Most Canadian parents using car seats that can face forward for backward usually turn them to face the front when a child is about one year old, or about 20 pounds (nine kilos). But this new study suggests a rear-facing seat can better help to avoid neck, chest and spinal injuries in toddlers in crashes.

British Drs. Elizabeth Watson and Michael Monteiro reviewed the U.S. National Highway Traffic Safety Administration's vehicle crash database, focusing on incidents involving 870 children between 1998 and 2003. They also looked at data from Sweden, where rear-facing children up to age four is common practice.

The researchers found that children up to 23 months sustained fewer injuries in any kind of crash when they were in seats facing backward.

Some toddlers who died in accidents while in forward-facing seats could have survived had they been facing the rear, the researchers say they found.

Toddlers seem to be at increased risk of severe injury when they're in front-facing seats in head-on collisions because of their relatively large heads, the authors contend.

"Excessive stretching or even transection (severing) of the spinal cord can result if a child is involved in a head-on crash while in a forward facing car seat. The younger the child, the lower the crash force required to cause spinal injury," they write.

Rear-facing seats are more effective at keeping the head, neck and spine aligned, distributing the force of the crash more evenly across those areas, they say. 

The authors say many parents and healthcare providers are unaware it is safer to leave children in rear-facing seats for as long as possible.

"Parents and guardians should be advised to keep young children in rear facing seats for as long as possible," the researchers conclude in their study, published on the website of the British Medical Journal.

They called on manufacturers and retailers to increase the availability of rear-facing seats for older children. They also called for a change to the current weight-range labelling of European seats, which suggest that forward- and rear-facing seats are equally safe for kids over 20 pounds.