Monitors allow these parents can get a good night's sleep

Spokesman, Foundation for the Study of Infant Deaths

It was thought that significant changes in these two could precede sudden infant death.

However, research published in the Journal of the American Medical Association (JAMA) suggests that this is not the case.

Not recommended

And in these circumstances, it adds, it would be inappropriate to continue recommending such monitors to parents.

The researchers looked at 1,079 infants in five US cities, monitoring them at home for a total of 718,358 hours in the first six months of life.

They found that long pauses between breaths, or a lengthy slowing of heart rate generally happened prior to the period between two and six months old customarily associated with SIDS.

This suggested that these physical phenomena were not immediate precursors of cot death.

Dr George Lister, one of the study's authors, said: "The difference in when extreme events most commonly occur and when SIDS is most likely to occur suggests that these events are not immediate precursors to SIDS, as was once thought.

"These events might be markers of vulnerability, rather than immediate indicators of SIDS."

An editorial in the journal by paediatrician Dr Alan Jobe said that "severe curtailing" of the use of such devices appeared to be justified.

Strategies advising parents to put newborns to sleep on their backs rather than their stomachs had already radically reduced the number of SIDS cases, he said.

"The residual causes of SIDS are unlikely to be prevented by home monitoring," he wrote.

Reassurance

However, the UK Foundation for the Study of Infant Deaths said that whatever the practical benefit of the monitors, they helped reassure parents who had already suffered one cot death, and were anxious about another.

A spokesman said: "Monitors allow these parents can get a good night's sleep.

"We would advise that they are properly briefed on what the monitors can do - and what they can't do."