Sudden Infant Death Syndrome

Sudden Infant Death Syndrome (SIDs) is the sudden death of an infant due to unknown/indeterminate causes – usually during the first 3 to 12 months. It is the major post-neonatal cause of death in developed countries, being the leading cause of sudden unexpected infant deaths (SUIDs). It commonly used to be called ‘cot death’. SIDS occurs during sleep. It is more common in Western countries (the rate is up to 10x more in developed countries).

Risk factors:
Sleeping on stomach;  overheating (eg close to heater; too many bedclothes);  use of formula feeding rather than breast feeding;  smoking during pregnancy;  drug addiction of mother during pregnancy; co-sleeping (increased risk for accidental suffocation); pre-term (<39 weeks of gestation); delayed or no prenatal care; lower birth rate; younger mothers; genetic (more common in boys).
No one risk factor in isolation is sufficient to cause SIDS.

The definition of SIDS is that it is currently unexplained, so the cause is not known or clear.

The “Triple-Risk Model” has been proposed and that is SIDS is considered to occur when the three conditions exist simultaneously:

  • Vulnerability: the infant has an underlying abnormality which reduces there ability to respond to low oxygen or high carbon dioxide blood levels (eg brainstem abnormality; pre-term; parents smoking).
  • Trigger: the infant is exposed to a triggering event (eg sleeping face down; infection; co-sleeping).
  • Timing: this vulnerability and triggering event occurs at a critical period in the infants development.

Clinical features:
Cyanosis;  fixed dilated pupils; pale, cool skin; absent respirations; absent pulse

Immediate management:
Quick and carefully examination and attempt resuscitation if any doubt. Otherwise leave the infant as found and contact ambulance. Remain until police arrive.
Grief support for families is important.

Differential diagnosis: accidental suffocation; shaken baby syndrome (child abuse); head injury; infanticide; MCAD deficiency; cardiac dysrhythmias; poisoning; anemia; carbon monoxide toxicity; hypothermia; long QT syndrome; hypoglycemia; infection (eg meningitis, pneumonia); inborn errors of metabolism.

The diagnosis based on the definition is that the death remains unexplained after exclusion of other causes, an autopsy and a death scene investigation.

Public health measures and campaigns have reduced the incidence – advice includes:
• place baby on back to sleep (unless there is a medical reason to sleep on side or stomach)
• keep the head uncovered during sleep
• keep baby’s environment smoke free
• breastfeeding and immunization are probably preventive

The American Academy of Pediatrics published updated guidelines in 2022 (link):

  • Babies should sleep on their back on a firm, flat, non-inclined surface free of soft goods, such as blankets and toys. These items, while appealing to many parents, can pose suffocation hazards.
  • The sleep surface should, at minimum, comply with all federal safety standards.
  • Any inclined surfaces, including car seats, strollers, infant carriers and infant slings, should be avoided for routine sleeping, especially for infants younger than 4 months.
  • Swaddling has not been shown to reduce the risk of SIDS. If babies are swaddled, they should always be placed on their back. Weighted swaddles or weighted objects within swaddles are unsafe. Swaddling should be stopped when a baby starts trying to roll over, usually at 3 or 4 months or earlier, as the swaddle can pose a suffocation hazard.
  • Parents should avoid devices marketed to reduce the risk of SIDS or other sleep-related deaths. There is no evidence for such claims, and they may lull parents into a false sense of security.
  • While there is no contraindication to using home cardiorespiratory monitors or wearable monitors, there is no evidence that using them will prevent SIDS. Families who decide to use these monitors should still follow the safe sleep guidelines.
  • Parents should sleep in the same room as baby, but not in the same bed.


  • Anti-vaccine cult members often use social media to comment on postings about SIDS cases to blame vaccines and blame the parents for vaccinating their infant. Some of this behavior is quite despicable and insensitive. The incidence of SIDS is lower in those who are fully vaccinated and that evidence is very clear.

Page last updated: @ 7:39 am

Comments are closed.