KEY POINTS:
Deaths of babies expected to be attributed to sleeping in bed with parents might be from far lighter contact than an adult actually rolling on top of them, researchers say.
Simply rolling against the baby, or the baby moving in its sleep and pushing against the adult, could be enough to endanger the infant's breathing, they said yesterday.
Wellington coroner Garry Evans has reserved his decisions after inquests into the deaths of seven babies whose mothers either had slept with them in the same bed or had put them to sleep on their tummies or on pillows.
Auckland University professor of physiology Alistair Gunn and colleagues told the Herald yesterday it was often presumed in such cases that an adult had inadvertently smothered the baby - and parents were understandably devastated by the implication.
"This may not be what happened.
"Our research, with x-rays of the newborns' upper airway, shows that babies' oxygen levels can be compromised even if the nose is not blocked.
"Unlike adults, small babies have a very mobile, unstable lower jaw, especially in sleep. Thus any pressure on the chin, even that produced by just bending the baby's head forwards so that the chin presses against the baby's own chest, pushed the large tongue backwards, narrowing the airway, with a fall in oxygen levels.
"Thus in these tragic cases, the parents may not have actually rolled on to the infant, but just pushed against the baby's chin - or indeed it could have pushed against them as baby moved in its sleep."
Smoking probably increased risks by dulling a baby's ability to wake when oxygen levels were low, said the researchers, including paediatrician Dr Shirley Tonkin, of the Cot Death Association.
The safest way for babies to sleep was on their backs in a bed or cradle of their own, in the same room as their parents, they said.
The wharekura (flax cradle), which was developed by Maori cot death expert Dr David Tipene-Leach and could be placed on a bed, was one safe option. Another was to use one of the cradles lent by some maternity hospitals, Sids (Sudden Infant Death Syndrome) and other organisations.
Auckland coroner Murray Jamieson said in 2005, after a number of baby deaths from "co-sleeping", that babies sleeping in their own bed was vital, even if it was just a banana box strengthened with tape and some extra cardboard.
The Health Ministry said at the time that bed-sharing could be safe if its guidelines were followed, but boxes or drawers should not be used.
