Parents are being warned against allowing their children to sleep in sitting or carrying devices, such as car seats, bouncers and swings.

According to US researchers, many parents allow their children to sleep in these devices, ‘not realising that there are hazards when they do this'.

They studied the records relating to 47 infants who had died while using these devices and found that all of the deaths except one were due to asphyxia, a condition which sees the body deprived of oxygen, for example, as a result of suffocation.

Two in three of the 47 deaths involved car seats, with just over half of these deaths being attributed to strangulation involving seat straps.

The rest of the deaths involved other devices such as bouncers, swings and slings.

The researchers emphasised that infants who are properly attached in a properly positioned car seat face minimal risk of suffocation-related injury. However, they emphasised that contrary to popular belief, these devices are not intended for unsupervised sleeping.

"Infants and young children should not be left unsupervised when using a sitting or carrying device due to the risk of suffocation and death," commented Dr Erich Batra of the Milton S. Hershey Medical Center.

The study noted that the time from when the infants were last seen alive to when they were discovered was as little as four minutes.

The researchers provide the following advice to parents:

-Do not leave infants unsupervised in these devices, awake or asleep
-Do not leave children in car seats with unbuckled or partially buckled straps
-Never place car seats on a soft or unstable surface
-Be aware that children in devices such as swings and bouncers can sometimes move into dangerous positions that could compromise their airways, even if they are correctly strapped in
-Infants should not be able to slump forward in a seat. Ensure restraints are used correctly
-Slings can be particularly dangerous because of the ease at which an infant's airway can be collapsed. The infant's face should always be ‘visible and kissable'
-Do not place more than one infant in a swing meant for one.

They added that infants should sleep on their backs on a firm mattress, with no loose bedding.

Details of these findings are published in The Journal of Pediatrics.