Scientists in the US found that babies under a year old who used a pacifier, also known as a dummy, while they slept had a 90% reduced risk of sudden infant death syndrome (SIDS) compared with other babies.

De-Kun Li, of the Health Management Organisation group Kaiser Permanente Northern California, said in a report published online by the British Medical Journal: "Use of a dummy during sleep was associated with a reduced risk of SIDS.

"Our results also provide some evidence that use of a dummy may reduce the impact of other risk factors for SIDS, especially those related to adverse sleep conditions."

Most cot deaths occur between two to four months of age and are more prevalent in boys than girls. The cause is unknown, but lying the baby down on its stomach, parental smoking and old mattresses, which may harbour toxic bacteria, have been cited as possible culprits.

A campaign to encourage parents to put infants to sleep on their backs has led to a significant fall in cot deaths.

Scientists from Kaiser Permanente and the National Institutes of Health questioned the mothers or carers of 185 infants who died of SIDS and 312 other infants of a similar age and race.

Dr Li said: "The use of dummies may be an effective strategy for public health intervention."

The American Academy of Paediatrics, which issued revised guidelines in October, recommends that babies are put to sleep only on their back and said pacifiers could be used to help prevent SIDS.