Scientists have made a major breakthrough into identifying a potential cause of Sudden Infant Death Syndrome (SIDS).
An Australian study shows brain samples of 55 babies who died of SIDS had reduced levels of a chemical in their brain, called Substance P, which helps to control head and neck movement.
The chemical also controls the response to low-oxygen situations, the research led by the University of Adelaide shows.
Lead author Dr Fiona Bright says while the exact cause of SIDS is yet to be identified, it does point to an "underlying vulnerability" which exposes some to an increased risk.
"That child is at greater risk of death because its body simply can't respond in the normal way," researcher Professor Roger Byard added.
The research could help to detect babies who are more susceptible to sudden death and put preventative measure in place, Prof Byard says.
"We really have opened a doorway into a whole new area of SIDS research. What we need to do now is work out why the levels are low and is there some way of testing these kids?"
Prof Byard says it also explains why babies who can't breathe don't try and help themselves out of the situation.
The chemical abnormality is particularly high in premature babies and boys.