SIDS Risk – The Triple Risk Model Explained

SIDS risk

SIDS Triple Risk Model is based on Scientific research that suggests SIDS (Sudden Infant Death Syndrome) events are most likely to occur if three things are going on at once.  

First Event

First, according to resent research published in The Journal of Pediatrics, there is mounting evidence that infants who die of SIDS have underlying vulnerabilities including genetic susceptibilities that put them at risk.  It is believed that babies with low serotonin levels lack the necessary trigger to respond to exogenous stressors. 

The SIDS Triple Risk Model suggest this brain abnormality, either genetic or developed during pregnancy, makes it hard for infants to easily wake up when faced with a potentially dangerous situation such as airway obstruction of rebreathing of harmful exhaled air.  

Want more information on what to do if your baby is sleeping face down, read our article – Baby Sleeping Face Down – What to Do.

Where babies who do not have this abnormality will turn their heads or move, these vulnerable infants simply sleep right through the dangerous situation and die.


The SIDS Triple Risk Model takes into account that all infants go through a critical brain growth phase.  This phase begins at one to two months of age but can last from one month through 12 month’s depending on the baby.  

Babies that may seem perfectly adequate at moving their heads when faced with a distressful situation may become vulnerable once they enter the critical brain growth phase. 


There is an outside stressor such as low oxygen or high levels of carbon dioxide.  Vulnerable infants either suffocate or rebreathe their exhaled air.

Their airway can be obstructed by sleeping face down on a fiber filled mattress, or they can create pockets of carbon dioxide by sleeping on their tummy with their head to the side by simply having their arm or hand up along side their face while on a solid or fiber filled surface.

Carbon dioxide or exhaled air can easily trap and accumulate on fiber filled mattresses, sheets, mattress pads, blankets, toys, bumpers, and cushions.  This is the part of the Triple Risk Model we actual have some control over.

What we do not know

There is no way to determine which infants have an underlying brain abnormality until death when an autopsy can be performed.  Also, there is no way to know when an infant begins or ends their critical brain growth phase, so according to the SIDS Triple Risk Model, all infants remain at risk (1).

Coordination and head control

Are babies that can roll or have good head control at less risk in regards to the SIDS Triple Risk Model?  No. The issue is not whether they have the muscle control to turn their heads & move.

The problem is they lack the ability to arouse themselves to get out of the situation of suffocation & positional asphyxia (rebreathing CO2). These vulnerable infants sleep right through it (2).

Back sleeping is best

We all know that back sleeping with no blankets is best.  Back sleeping and non-smoking parents insure baby has fresh oxygen.  Breast-feeding and pacifier use help to prevent baby from sleeping too deeply where they cannot arouse themselves if they have airway obstruction (low oxygen) or they are rebreathing their carbon dioxide (exhaled air).

Sleep can actually be a dangerous thing for some babies

Everyone breaths in oxygen and breathes out carbon dioxide. The SIDS Triple Risk Model is based on studies that show babies are more likely than adults to trap exhaled air (carbon dioxide) around their face when they lie on their stomach on fiber filled surfaces. 

Even if their head is turned to the side especially if their arm or hands are close to their face, or they have their face covered by a blanket, bumper pad, or even a soft mattress pad, during sleep. 

The SIDS Triple Risk Model explains that Instead of breathing in fresh oxygen, these infants rebreathe the carbon dioxide they just exhaled.  This causes their oxygen level to drop and carbon dioxide levels to climb. 

If carbon dioxide levels become too high, most babies will wake up enough to move their head, and take in clean oxygen. The SIDS Triple Risk Model suggest babies die of SIDS if they can’t wake up to react to these abnormal low oxygen and high carbon dioxide levels. 

This inability to wake up easily and react quickly when there isn’t enough oxygen is what makes a baby a “vulnerable baby” (3).

Who is vulnerable?

We have no way to know which babies, upon birth, are going to be vulnerable to SIDS.  There is no test to give us this information.  Nor can we control any aspect of the critical brain developmental period that all babies must go through.

The only factor of the SIDS Triple Risk Model we can control is reducing the carbon dioxide build up and increasing fresh oxygen.  That is why scientific research has now turned to “what a baby sleeps on.” 

The American Academy of Pediatrics currently recommends a firm sleep surface to avoid the accumulation of carbon dioxide.  However, the American of Pediatrics is now exploring the increased published scientific data proving that air permeable or breathe-through surfaces as the recommendation since they do no trap carbon dioxide and they promote fresh air even if a baby is lying face-straight-down(4,5,6)

Find out more about the warning signs of SIDS.  Read our article, Are There Warning Signs of SIDS?

Retrospective analysis vs scientific studies

One thing that is important to clarify, is the research conduct by the American Academy of Pediatrics Safe Sleep task force members is based on retrospective analysis.  What this means is, all their research is based on death scene investigations. 

The research is not “forward” research that searches for safer products or alternatives, they just make recommendations based on either past events or other published scientific research. 

The problem is, using retrospective analysis is difficult because parents, and death scene investigators are not mandated to report incidences to the Consumer Product Safety Commission. 

Also, there has been no standardization in death scene investigations.  The cause of death is what ever the medical examiner calls it.  One examiner may conclude the cause of death to be positional asphyxiation and another could conclude that the same death is SIDS. 

Currently, only half of the states in the US have guidelines for death scene investigation of Sudden and Unexplained Infant Deaths.  

SIDS versus sleep related deaths

“SIDS” is a subset of “sleep-related deaths.”  Sleep-related deaths include deaths due to known causes – suffocation, entrapment, overlay, etc.

Some SIDS deaths are unpreventable, but it is a small percentage. A large percentage of infant sleep related deaths are preventable.  

In a study of 209 sudden unexpected infant deaths with in-depth death scene investigations, the medical examiners identified asphyxia as either the cause or potential cause of death in the majority (86%) of cases (1).  Asphyxia is associated with carbon dioxide rebreathing.

If the death has a know cause of low oxygen and/or high carbon dioxide, the death is labeled suffocation or positional asphyxiation.   However some sleep related deaths are still called SIDS if the “stressor” (cause of low oxygen or high carbon dioxide) cannot be conclusively determined. 

Also, carbon dioxide is not detectable in human tissue, so some deaths that are believed to be asphyxiation (a form of suffocation) are still labeled as SIDS deaths. 

Find out more on how to prevent SIDS.

QT syndrome and Fatty Acid Oxidation Disorder

Two example of SIDS deaths that are NOT from low oxygen or high carbon dioxide are QT syndrome and Fatty Acid Oxidation Disorder. 

QT syndrome causes an abnormality in heart rhythm and Fatty Acid Oxidation Disorder is where the body doesn’t properly break down fats into sugars, this causes blood sugar levels to become very low, causing death. 

This explains why some infants will fall victim to SIDS even if they are in a safe sleep environment and sleeping on their back.  These types of deaths are not part of the SIDS Triple Risk Model.

Back sleeping is best

It is no mystery that the safest way to place a baby to sleep is on her back, but what about when your baby inadvertently rolls to the prone or tummy sleeping position?  Air permeable/breathe-through crib mattresses are scientifically proven as safer than fiber filled crib mattresses for the vulnerable infant that rolls over.

Air permeable/breathe-through crib mattresses do not trap harmful carbon dioxide and they keep fresh air circulating around your baby even if your baby is face straight down.  The one factor in the Triple Risk Model that we can control is the elimination of carbon dioxide accumulation for sleeping infants. 

The SafeSleep Breathe-Through Crib Mattress has been scientifically tested and proven to significantly reduce carbon dioxide retention, so a sleeping infant – even if face straight down – will not be at risk of rebreathing their exhaled air (carbon dioxide).


  1.  Duncan, Othon J. Mena, Henry F. Krous, Felicia L. Trachtenberg and Hannah C. Bradley B. Randall, David S. Paterson, Elisabeth A. Haas, Kevin G. Broadbelt, Jhodie Kinney,  Potential Asphyxia and Brainstem Abnormalities in Sudden and Unexpected Infant Death:  Pediatrics 2013;132;e1616; originally published online November 11, 2013; DOI: 10.1542/peds.2013-0700
  2. Paluszynska DA, Harris KA, Thach BT. Influence of sleep position experience on ability of prone sleeping infants to escape from asphyxiating microenvironments by changing head position. Pediatrics, Dec. 1, 2004.
  3. Hannah C. Kinney,1George B. Richerson,2 Susan M. Dymecki,3 Robert A. Darnall,4,and Eugene E. Nattie5 Brainstem and Serotonin in the Sudden Infant Death Syndrome: Annu Rev Pathol. 2009; 4: 517–550. doi:  1146/annurev.pathol.4.110807.092322 PMCID: PMC3268259 NIHMSID: NIHMS34795
  4. Patrick L. Carolan, MD; William B. Wheeler, MD; James D. Ross, RRT, RCP; and James S. Kemp, MD, (2000), Potential to Prevent Carbon Dioxide Rebreathing of Commercial Products Marketed to Reduce Sudden Infant Death Syndrome Risk, Pediatrics, 105:4 774‐779
  5. Bar‐Yishay, E., Gaides, M., Goren, A. and Szeinberg, A. (2011), Aeration properties of a new sleeping surface for infants. Pediatr. Pulmonol., 46: 193–198. doi: 10.1002/ppul.213516.
  6. Intertek, CPSC testing lab study on an air permeable/breathe-through crib mattress; Carbon Dioxide Rebreathing Assessment; 2010 

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