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Facts about Cot Death





Facts about Cot Death

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What is Cot Death?

Cot Death, more correctly known as Sudden Infant Death Syndrome (SIDS), was defined in 1969 as "the sudden death of an infant or young child which is unexpected by history and in which a thorough post mortem examination fails to demonstrate an adequate cause for death". The term "SIDS" has since been widely used on death certificates although in the past ten years "unascertained" and "sudden unexpected death in infancy" have also become common. "Cot Death", however, is still the term understood and used by most people in the UK.

How common is Cot Death?

Until 1991 the rate in Scotland was approximately 1 in 500 livebirths, similar to that of other developed countries. Since then the rate has gradually decreased and is now around 1 in 1,500 livebirths, a drop also noted in other parts of the world. Although we cannot be certain of the cause of this decrease it is probable that avoiding placing babies on their fronts to sleep has made a major contribution. However, Cot Death remains the biggest single cause of death in infants aged between one week and one year.

What happens when a Cot Death occurs?

In the typical case an apparently healthy infant is put down to sleep without the slightest suspicion that anything is out of the ordinary, although there are sometimes signs of a slight cold or tummy upset. When next checked the infant is found to be dead. Sometimes the time interval is only minutes. Sometimes the baby has not even been sleeping - there are accounts of infants dying in the middle of a feed. There is no sound or sign of a struggle, or of any distress.

Are some babies at more risk?

Although the basic cause(s) of Cot Death are unknown there are certain characteristics which have been confirmed by a large number of different studies.

Age Distribution

A small number of Cot Deaths occur in the first month of life. The incidence rapidly rises, after that, reaching a peak in the second and third months. 83% of Cot Deaths occur in the first six months and only about 5% in babies aged 9-12 months. A very small number of Cot Deaths, 3-4%, take place in the second year of life.

Sex Incidence

There is a clear sex difference in SIDS with a male to female ratio in Scotland of approximately 2:1. This is in sharp contrast to other causes of infant death after one week of age which affect an almost equal number of boys and girls.

Seasonal Incidence

Cot Death is more common in winter than in summer - approximately 60% of deaths occur in winter/spring compared with 40% in summer/autumn.

Birth Order

Second and later born infants in a family are at greater risk than first born.

Maternal Age

Young mothers (under 20 years old) are more likely to lose a baby to Cot Death than older mothers. The average age of Cot Death mothers is two years younger than the general maternal population.

Obstetric Factors

Preterm, low birth weight babies are more likely to die from Cot Death than full term infants. Twins are also more vulnerable.

Socio-Economic Factors

Cot Death is more common with deprivation but occurs in families at all social levels. There is unanimous agreement that maternal smoking increases risk, particularly during pregnancy, resulting in a seven-fold risk when the mother smokes over 20 cigarettes per day. Smoking by parents and other household members after the baby is born also increases the risk. The infants of drug-abusing mothers are more vulnerable to Cot Death.

Infant Care Practices

There is now considerable evidence that placing babies to sleep on their fronts increases the risk of Cot Death. Side sleeping also appears to be less safe than back. Overheating may make a baby more vulnerable and several studies have shown that babies whose heads are accidentally covered with bedding are at greater risk. Breastfeeding does not appear to protect against Cot Death, although it has many other benefits.

What causes Cot Death?

For centuries babies commonly slept in their parents' bed and it was believed that sudden unexpected deaths were due to suffocation by overlaying. By the nineteenth century doctors began to question this assumption and since then research has been carried out in a wide variety of fields including pathology, physiology, epidemiology and risk reduction. It is anticipated that no single area of study will provide the final answer but each may contribute to our understanding of what causes these babies to die.

Can we prevent Cot Death?

Since we do not know why Cot Deaths occur, we cannot prevent them. However, research has indicated that the risk may be reduced if the following steps are taken:

  • Place baby to sleep on the back
  • Avoid smoking during pregnancy and after birth keep baby in a smoke-free room
  • Avoid overheating baby
  • Keep baby’s head uncovered – place baby’s feet at the bottom of the cot
  • Consult a doctor if baby seems unwell

Was anyone to blame?

In Scotland when a Cot Death occurs it is routinely reported to the Procurator Fiscal - as is the case with any sudden, unexpected death - and the Fiscal will order a police investigation and a post mortem examination. While this is an inevitable part of our legal system it can be very distressing for the parents and can make them feel as if they are under suspicion.

Equally distressing and bewildering is the lack of an explanation for the death. With no reason and no-one else to blame, parents often blame themselves, feeling that they must have done, or failed to do, something which led to the death. It is important to emphasise to parents that Cot Death is unforeseen and therefore unpreventable. The vast majority of Cot Death babies have been lovingly cared for. Occasionally the baby will have been seen by the family doctor shortly before the death because of some slight ailment such as a cold. Nothing has been found which would have indicated a need for serious concern or have led anyone to anticipate a sudden death.

Did the baby choke?

Sometimes parents worry that their baby smothered or choked. While it is possible for an infant to smother accidentally, this is rare. Cot Death is also not caused by vomiting or choking. Sometimes milk or blood-tinged froth is found around the nose or mouth. This occurs during or soon after death and is not the cause of death.

Can it happen again in a family?

Parents naturally fear a recurrence. However, Cot Death is not hereditary and any future babies in the family may run only a very slightly increased risk of recurrence, of the order of 2-5 times the population rate.


The Scottish Cot Death Trust, Royal Hospital for Sick Children, Yorkhill,
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