Some babies who die from cot death may have stopped breathing because they are dreaming about being back in the womb, says a new theory.
Babies should be put to sleep on their backs
A new book from Australian brain researcher George Cristos says that the dream may be so convincing that the baby's body functions revert to a pre-birth state.
In the womb, a baby is suspended in fluid and all its oxygen is supplied from the mother - there is no need for the baby to breathe.
However, cot death experts in the UK say they are "not aware" of any evidence pointing to this as a cause.
The rate of cot death has plummeted in many countries following the introduction of safety advice for parents, including the need to lay babies on their backs to sleep.
However, in approximately half of all sudden infant deaths, the cause of death has yet to be uncovered.
The majority of cot deaths occur before the baby is six months old.
There are many theories as to why these babies may be vulnerable.
Dr Christos, a lecturer in mathematics and physics at Curtin University of Technology, who also has a research interest in learning and memory, puts forward his theory in a book, "Memory and Dreams: The Creative Human Mind".
He points to research in the US in which people reported stopping breathing when dreaming about swimming underwater.
He said that babies had up to eight hours of "rapid eye movement" sleep - the type associated with dreaming in adults - a night.
He writes: "What could a baby dream about? Well, it could dream about its life in the womb."
He said that his theory could help explain why babies who sleep face down might be at higher risk - because they would adopt a more "foetal" position which might be more likely to trigger dreams of their time in the womb.
It may prove difficult to prove such a theory - little is known about the dreaming of infants, and some experts have suggested that they may not have dreams in the conventional sense in their earliest months.
Dr Robin Campbell, a lecturer in psychology from the University of Stirling, whose research interests include dreaming in children, described the theory as "potty".
He says that research suggests that classic "acting out" dreams - in which a person believes that he or she is at the centre of events - do not start to happen until years after birth.
He told BBC News Online: "You simply can't say that babies have dreams in the same way adults do.
"There is no evidence to support this theory at all."
The Foundation for the Study of Infant Deaths said that parents should take heed of existing, effective ways to lessen the risk.
A spokesman said: "No one knows what causes cot death.
"It is likely to be a number of factors coming together at a particularly vulnerable stage of a baby's development.
"FSID is not aware of any research evidence for a "dreams" theory.
"If parents want to follow research-proven advice on how to help reduce the chances of cot death, they should sleep babies on their back, don't smoke, and don't let them get too warm."