Sudden infant death syndrome Dr Trisha Macnair Sudden infant death syndrome, or cot death, is a term used to describe the situation when a baby dies suddenly for no apparent reason. This may occur at any time, not just at night in a cot.

In this article

What causes it? Who's affected?

What are the symptoms? How is it diagnosed?

Can the risk be reduced?

The cause of cot death isn't known, but it's suspected that there may be many different problems, or combinations of problems, that can lead to it.

Infections, environmental contaminants or, more rarely, an inherited genetic problem may all be important factors, especially if the baby is exposed to them at a stage when they're still immature and less able to deal with stress.

Each week in the UK, seven babies die from cot death

Each week in the UK, seven babies die from cot death, a drop of 75 per cent since the Back to Sleep campaign was launched in 1991. The majority of deaths are in babies under six months.

Although the cause is unknown, some factors seem to increase the risk, including putting the baby to sleep face down, exposure to cigarette smoke, overheating and sharing a bed with parents, especially if they've been eating or drinking (although in some cultures sharing a bed doesn't seem to increase the risk).

The risk is also higher among families living in difficult social circumstances. It's rare for cot death to occur twice in the same family.

In general, the babies appear to die peacefully in their sleep without distress or previous warning symptoms.

Occasionally, babies are found blue and not breathing - although if they are close to death they can be successfully resuscitated.

The sudden unexpected death of a small child is always fully investigated by the coroner, with a post mortem.

The following advice can help to reduce the risk of cot death:

• Put your baby on their back to sleep
• Don't smoke during pregnancy (this applies to both parents)
• Don't allow other people to smoke in the same room as your baby
• Don't let your baby get too hot
• Keep your baby's head uncovered - their feet should be to the foot of the cot to stop them wriggling down under the covers
• Never fall asleep with your baby on a sofa or in an armchair
• Don't share your bed with your baby if you or your partner smoke, have been drinking alcohol, are taking drugs or medication that makes you drowsy, are excessively tired, or if your baby was premature or small at birth
• Put your baby's cot in your bedroom for the first six months

This article was last medically reviewed by Dr Rob Hicks in July 2006.