Child abuse is not a major cause of sudden infant death, according to a study.
Babies should be put to sleep on their backs
Previous research has suggested that as many as 40% of cases of sudden infant or cot death may be a result of deliberate abuse.
However, a new study by a doctor in the north of England suggests the true figure may be much lower.
Her study estimates that between 3% and 10% of sudden infant deaths may be murder.
High profile cases
The findings follow two recent high profile court cases in which medical evidence on cot death has come under the spotlight.
Trupti Patel, from Maidenhead, Berkshire, was found not guilty in June of murdering three of her children.
Medical experts suggested the children may have suffered from a genetic disorder. The prosecution's case had centred on the claim that cot death does not run in families.
In January, Sally Clark, the 38-year-old solicitor from Wilmslow, Cheshire, who had been jailed for life in 1999 for murdering her two sons, had her conviction quashed.
Judges said medical evidence suggesting that two cot deaths in one family is rare was unreliable.
This latest study by Dr Dolores Stanton, a retired consultant paediatrician, raises further doubts about reliability of medical statistics in this area.
She examined 72 cases of sudden infant death in north and east Yorkshire between 1982 and 1996.
The age of the infants at death ranged from less than 28 days to 27 months.
The cases involved 69 families, three of whom had lost two children each.
Of these, two had been suspected of deliberately harming their children.
In both cases, there had also been reports of an alleged apparent life-threatening episode in the early months of the second child's life.
This is regarded as a possible warning sign of abuse.
Of the remaining families, three had children placed on protection registers after the sudden death of an infant.
Overall, there were suspicions of possible abuse in five families.
However, according to Dr Stanton, just two families lost babies "in circumstances suggestive of maltreatment".
There were no concerns about the remaining families, most of whom were closely monitored until 2000.
Collectively, they gave birth to a further 93 children and there was never any evidence that these were being harmed.
Dr Stanton said the figures suggested that the proportion of cases where abuse is the cause of sudden infant death may be much lower than previously thought.
A study in 1993 by Professor John Emery claimed that between 10% and 20% of sudden infant deaths were actually murder.
But Dr Stanton said: "Four unexpected deaths in two local families can be considered a 6% rate of suspected non-accidental death."
Dr Stanton added that sharp falls in sudden infant deaths in recent years would suggest that a higher proportion of deaths are now actually murder.
The number of deaths have fallen sharply over the past decade as more and more parents followed advice to always put babies to sleep on their backs.
Writing in the journal Archives of Disease in Childhood, she said: "There is no evidence that the fall in the overall SIDS rate has increased the relative proportion of the minority who have been allegedly maltreated."
However, Dr Stanton said that where there were suspicions of maltreatment after the sudden death of one child they must be addressed.
But she added: "Otherwise, families require compassion after their loss and support for subsequent siblings.
"Comprehensive child protection can be reserved for the few."
Chris Bacon, a paediatrician and medical advisor to the Foundation for the Study of Infant Deaths medical advisor, said: "It is important that all sudden infant deaths are investigated thoroughly, both to distinguish more effectively between natural and non-natural deaths, and to learn as much as possible about the causes of natural deaths."