Very young babies are vulnerable to sudden death, when seated, warns a study published ahead of print in the Archives of Disease in Childhood.
Babies less than a month old are most at risk, the research indicates.
The researchers base their findings on an analysis of all sudden unexpected deaths occurring among babies up to 12 months of age in the Canadian Province of Quebec between 1991 and 2000.
In all, 534 babies died during this period, but the cause of death was fully investigated in only 508.
In 99 cases, the cause of death came to light after further investigation, but in 409 cause of death remained unexplained.
Seventeen (3.3%) of the 508 deaths had occurred in babies who were seated, predominantly, but not exclusively, in car seats. Ten of these were unexplained
Premature babies were not at greater risk. But those aged under a month, were almost four times as likely to die suddenly while seated as were older babies.
And babies under one month old in the group of unexplained deaths were more than seven times as likely to die while seated.
The authors point out that their research indicates that the rate of deaths among seated babies is relatively small at just over 3%. And there are no questions about the necessity or safety of car seats.
Instead, extra care should be taken for very young babies in any type of infant seat, they say.