Frequently Asked Questions About Crib Death (SIDS)

What is crib death (SIDS)?
Crib death (SIDS) is the most common cause of infant death in many Western countries. In most cases the baby has been put down to sleep in his or her crib and later found lifeless, with no sign of illness or physical struggle. Crib death can also occur in other situations which parallel "crib situations," or which are sleeping environments, for example: strollers, carseats, playmats, sofas, and adults' and children's beds.

What is the crib death risk age?
If a baby was born at full term, with a normal birth weight, and does not experience any significant health problems, the risk age can be regarded as over at one year. If any of those situations does not apply (for example, if the baby was premature), the risk age can extend out to fifteen months.

What is the cause of crib death?
C rib death is caused by highly toxic nerve gases which can be generated from mattresses and other bedding used in babies' cribs. The gases are generated by action of common household fungi on compounds of phosphorus, arsenic and antimony present in the mattress or bedding.

How can crib death be prevented?
By preventing exposure of the baby to the toxic gases which cause crib death. This is done by wrapping the baby's mattress in accordance with a specified protocol (to separate the baby from gas generation in the mattress) and using specified bedding (so that the gases cannot be generated on top of the wrapped mattress). For information on how to wrap a baby's mattress for crib death prevention click on the sidebar heading How to Prevent Crib Death.

Why do crib death babies show no symptoms?
The toxic gases which cause crib death are anticholinesterase agents. They depress the baby's central nervous system, resulting in cessation of the heart and lung functions. Babies who die of crib death are not "ill" in the medical sense; they are poisoned by environmental gaseous poisoning.

What is a "near miss"?
A "near miss" occurs where a baby has been seriously affected by the toxic gas/es which cause crib death but is still alive. The baby's heart and lung functions may have stopped. "Near miss" babies often have blue lips (indicating shortage of air). If at this stage the baby is picked up and air is blown onto his or her face, the baby may start breathing again. If a partly poisoned baby is moved into fresh air and can be made to breathe, the baby usually survives.

What research has been done into the toxic gas theory for crib death?
A large amount of research relating to the toxic gas theory has been published in peer-reviewed scientific journals. Every step in the fungal generation of toxic gases from infant bedding has been proved. Mattress-wrapping for crib death prevention is supported by wider research than supported the introduction of various items of traditional advice (including face-up sleeping). For more information about research, click on the sidebar headings Research and Statistics.

Didn't the 1998 UK Limerick Report disprove the toxic gas theory for crib death?
No. For more information about the Limerick Report click on the sidebar heading Limerick Report.

Didn't the UK CESDI Study find that three babies in Britain died on polythene-wrapped mattresses?
No. There is no evidence that these mattresses were wrapped in polythene. For such a claim to be valid, chemical analysis of the plastic was required; however no such analyses were carried out. In February 2000 Professor Peter Fleming (an author of the CESDI Study) conceded that the CESDI study had not demonstrated that the mattresses on which the babies died were wrapped in polythene.

Why are recently vaccinated babies and babies with infections at higher risk of crib death?
The fever which results from infection and which can also follow vaccination results in increased temperature in the baby's crib. If bedding in the crib is capable of toxic gas generation, a rise in temperature of (for example) three degrees Celsius in the crib can result in a tenfold increase in the rate of gas generation.

Why does the risk of crib death rise from one baby in a family to the next?
Many parents re-use crib mattresses from one baby to the next. If a mattress contains phosphorus, arsenic or antimony and certain household fungi have become established in the mattress during previous use by another baby, generation of toxic gas commences sooner and in greater volume when the mattress is re-used for the next baby.

Why do babies of single parents have a very high crib death rate?
For economic reasons, solo parents are more likely to sleep their babies on previously used mattresses which they have acquired secondhand. The risk of crib death increases as a mattress is re-used from one baby to the next.

Why does overheating increase crib death risk?
The extra warmth in the baby's crib causes the fungus to increase gas generation. A rise in temperature of three degrees Celsius in a baby's crib can cause gas generation to increase tenfold or more.

Why do more crib deaths occur in winter than in summer?
During winter babies frequently use more bedding, resulting in greater risk of overheating in the crib and thus greater risk of gas generation. Also, windows and doors are more likely to be closed during winter, decreasing ventilation around the baby's crib. As a result, drafts which could cause gases to disperse are reduced or eliminated.

Why does face-up sleeping reduce the risk of crib death?
The gases which cause crib death (phosphines, arsines and stibines) are all more dense than air. They diffuse away from a baby's mattress towards the floor, so a baby sleeping face-up is less likely to ingest them.

Why does bedsharing between adults and babies pose crib death risk?
Adults' mattresses frequently contain the same chemicals and fungi as babies' mattresses, and therefore can generate the same toxic gases. For physiological reasons adults are not put at risk by this gas generation in beds, but a bedsharing baby can die within a short period of time.

Why do pacifiers appear to reduce crib death risk?
Mothers who wish to use a pacifier will very often sleep the baby face-up so that the pacifier stays in place. And face-up sleeping reduces the risk of crib death, because the gases which cause crib death are more dense than air and a baby sleeping face-up is less likely to ingest them. So it is not the pacifier which reduces crib death risk, but rather the statistical likelihood that the baby using the pacifier will be sleeping face-up.

Crib death rates in various countries fell during the 1990s but have now levelled out and are no longer falling. Why is this?
In most countries these reductions in crib death rates were the result of face-up sleeping campaigns. However, for reasons relating to the chemistry of the gases which cause crib death, face-up sleeping is only a partial preventive. In particular, it is not very effective against the danger posed by phosphine. As a result, all face-up sleeping campaigns (wherever they occur) achieve a reduction of around 45-50% in the crib death rate, at which point the rate hits a plateau and does not fall further. This plateau has now been reached in the US and Canada.

In many countries where there is an indigenous or minority population, that group has a much higher crib death rate than the local European population. Why is this?
Crib death has a strong socio-economic bias, because less well-off parents are much more likely to use secondhand or previously used mattresses for their babies. Since, therefore, indigenous or minority populations are frequently in low income groups (e.g., Canadian Indians, Australian Aborigines, and Maori New Zealanders), these groups also have very high crib death rates. In addition, some indigenous or minority ethnic groups (e.g., Maori New Zealanders) traditionally bedshare with their babies, and adults' mattresses are by definition re-used mattresses.

How does the toxic gas theory explain crib deaths which occur in adults' arms?
If a baby has been lying in a crib or on some surface where he or she has been exposed to a lethal dose of toxic gas, and as a result the mechanism of death is already occurring when the baby is picked up, the baby can die while being held in the adult's arms. Also, crib death can occur in an adult's arms if a baby is picked up and held in an item of bedding which is generating toxic gas.

Is crib death cause by babies re-breathing their exhaled carbon dioxide?
No. All babies exhale a similar amount of carbon dioxide, regardless of whether they are first, second, third, or later babies in a family. Therefore, the statistical finding that the crib death rate rises from one sibling in a family to the next disproves the carbon dioxide theory.

Does crib death have any medical or physiological cause?
No. For more information on this topic click on the sidebar heading Crib Death: No Medical Cause.

Autopsies have shown that crib death babies frequently have bacterial and fungal infections in their throats and lungs. Why is this?
The conditions in the baby's bedding which favored the growth of fungi generating toxic gases would also have favored the growth of other micro-organisms, which the baby has then breathed in. Many of these other micro-organisms would be harmless, but they would still be noticeable in an autopsy.

Why aren't there many crib deaths among babies less than one month old?
A significant number of babies sleep on new mattresses, and it takes around one month for fungi capable of gas generation to become established in a mattress. However, a baby less than one month old can die of crib death if he or she is placed on a mattress which has recently been used by another baby and is already capable of generating toxic gas.

Why do relatively few crib deaths occur among babies over six months old?
An older baby is more able to respond physically to the initial distress which is caused the exposure to the toxic gases. An older baby experiencing this distress (e.g., the initial headache which occurs) can take action by flailing around in the crib , throwing off bedding, or sitting or standing up in the crib. This attracts the attention of adults. It also disperses gases from around the baby; or physically removes the baby from the gases (if the baby sits or stands up in the crib), since these gases are more dense than air.

Why is the crib death rate higher for twins than for singleton babies?
First, if the twins are not the mother's first pregnancy, often the mother already has a crib mattress. Secondly, many twins sleep in the same crib when they are very young babies, but at some point while still within the crib death risk age are separated so that they are sleeping in separate cribs. Both of these situations require a second mattress to be obtained. As a consequence, it often occurs that one twin in a family sleeps on a previously used mattress, while the other twin sleeps on a new mattress. This has the result that the crib death rate among twins is significantly higher than among singleton babies; also it is statistically much more likely that one twin will die of crib death than the other. The twin sleeping on the re-used mattress is at around double the crib death risk of the twin sleeping on the new mattress.

Given that millions of unwrapped mattresses contain phosphorus, arsenic or antimony, why aren't there more crib deaths?
In order for crib death to occur, the following circumstances must co-exist in the baby's crib :
1. The mattress (or other bedding) beneath the baby must contain phosphorus, arsenic or antimony.
2. The condition of the mattress or bedding must support fungal growth (for example, be damp with sweat or milk, or contaminated with urine).
3. Fungi capable of generating gases from phosphorus, arsenic and antimony must be growing in the mattress or bedding.
4. The fungi must be sufficiently active to produce a lethal dose of the gases.
5. The baby must ingest a lethal dose (for example, because the baby is sleeping face down, or because there is insufficient ventilation around the baby to disperse the gases).
It is uncommon for all these circumstances to co-exist in a baby's crib. Many babies are exposed to sub-lethal doses of toxic gas/es in their cribs, and no immediate harm results. Occasionally, however, all the above circumstances do co-exist and a crib death ensues.