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When Can a Baby Sleep on Their Stomach?

When can a baby sleep on their stomach

When Can a Baby Sleep on Their Stomach?

Are you finding your baby sleeping on his stomach?  A panic feeling that comes over you when you find your baby has rolled in the middle of the night and is now sleeping on his stomach.  The panic feeling is worse when you find them face down

So, when can a baby sleep on their stomach so both of you can sleep better?  

We all hear the safe sleep warnings against placing babies on their stomach.  There is an abundance of research supporting placing an infant on his back to reduce the risk of Sudden Infant Death Syndrome (SIDS). 

What isn’t Clear, is When Can a Baby to Sleep on Their Stomach?

Unfortunately, parents are falsely assured from many sources, including pediatricians, that once their baby is strong enough to roll over, it is safe for their baby to sleep on their stomach. 

Using research-based evidence and compelling insight into the following topics, we navigate facts from fiction to determine when it is safe for your baby to sleep on their stomach.

Why Back Sleeping is Best

We know back sleeping is safest, but you may not know why.  According to the AAP Safe Sleep Task Force, “asphyxia is long been considered the primary cause of death in many instances of SIDS.  Frequent autopsy findings of pulmonary edema, often identified with asphyxia, are found with many SIDS deaths.  The practice of back sleep is known to protect against SIDS.   


Infants sleeping in a prone position or lying on or near a soft blanket or other soft bedding can rebreathe exhaled carbon dioxide.  Rebreathing leads to hypercarbia and hypoxia.  Hence, if the environment of infants does not change or infants are unable to escape the dangerous situation, they will ultimately die of asphyxia. (JAMA Pediatrics February 2017 Volume 171, Number 2)


Asphyxia occurs when oxygen is insufficient in the human body.  When an infant begins to rebreathe his exhaled air, he slowly deprives himself of oxygen.  Eventually, the constant re-breathing of carbon dioxide suppresses the infant’s breathing needs, leading to hypercarbia.


Hypercarbia is a condition of abnormally elevated carbon dioxide levels in the blood. Carbon dioxide is a gaseous product of the body’s metabolism and is usually expelled through the lungs.  Therefore, when carbon dioxide accumulates in the body, it leads to hypoxia.


Hypoxia is insufficient oxygen in the tissues to maintain physical function.

The belief is infants who;

  • sleep on their stomach,
  • sleep on soft bedding,
  • use a blanket,
  • have stuffed toys in their crib,
  • have bumper pads attached to their crib,
  • sleep with others,
  • have anything close to their face (including their hands and arms),

Are at increased risk of SIDS since these sleeping situations can trap harmful carbon dioxide.

Back sleeping and rebreathing

When infants sleep on their back without a blanket, there is a much lower risk anything can trap carbon dioxide.  Consequently, making it unlikely for an infant to constantly rebreathe his exhaled air.

In order for infants to safely sleep on their stomach, we must eliminate the risk of trapping carbon dioxide.  If we eliminate trapped carbon dioxide, infants cannot rebreathe it. 

Unfortunately, most crib mattresses trap carbon dioxide.  Traditional crib mattress designs contain fillers, vinyl coatings, quilted tops or solid coverings to prevent contamination. These fabrics and fillers all trap deadly carbon dioxide.

What is Rebreathing?

Rebreathing is when an infant lies face-down or near-face-down on his stomach, air is trapped around the baby’s nose or mouth. This causes the baby to breathe more CO2 than oxygen. If the baby does not wake up or react appropriately, it can lead to death.

Watch Professor David Greenblatt video for a visual on rebreathing.

After our analysis, we will introduce you to one crib mattress scientifically tested to eliminate the risk of rebreathing carbon dioxide even if  an infant is in a face-down position.  

Why Some Infants Who Sleep on Their Stomach are at Higher Risk

Most of us know the frightening feeling of a heavy blanket or pillow over our faces.  This feeling forces a natural trigger to remove the object blocking oxygen.  In addition, we do not worry about sleeping on our big fluffy pillows, pillow-top mattresses with our down quilts.  Why?  Because we have an innate sense to turn our head, even in deep sleep, when our breathing is compromised by the accumulation of carbon dioxide. 

Like adults, most infants turn their heads or fight to get something off their faces when carbon dioxide begins to cause breathing difficulties.  But unfortunately, some infants do not!  

A crib mattress eliminating the buildup of carbon dioxide saves lives.

Serotonin and rebreathing

In 2010, a group of scientists discovered the first direct correlation between SIDS / SUID deaths and serotonin levels.  This finding was discoverd by studying the brain stems of infants who died suddenly and unexpectedly.   

Serotonin is a brain chemical that conveys messages between cells and plays a crucial role in regulating breathing, heart rate and sleep.  Researchers theorize serotonin abnormalities reduce an infant’s “ability to respond to breathing difficulties, including low oxygen levels or high carbon dioxide levels. The leading scientist suggests SIDS is the result of infants rebreathing carbon dioxide accumulation in thier bedding and on their mattresses while sleeping on thier stomach. 

Dr. Hannah Kinney, “Babies who died of SIDS had abnormalities in serotonin in reigns of the brain stem that control breathing heart rate and blood pressure during sleep.”  When a baby is put face down in a bed, it begins to rebreathe carbon dioxide, which is toxic.

Several studies have followed, linking high serotonin levels in the blood of SIDS infants and deficiencies in serotonin receptors. These studies report a common result: reflex apnea and arousal reactions that lead to an infant’s inability to respond to rebreathing of carbon dioxide. In brief, some infants simply do not respond when they are in danger of rebreathing of their exhaled air!

Although the link between serotonin and SIDS / SIDS / SUID is a major finding in 2010.   More than ten years later, we still have no way of testing live infants to determine their serotonin levels, serotonin abnormalities, reflex apnea or arousal reactions. Consequently, all infants are at risk of rebreathing lethal carbon dioxide if they sleep on their stomach on a mattress that does not allow carbon dioxide to dissipate, or if they are in an unsafe sleep environment.

A crib mattress that eliminates carbon dioxide before an infant takes in their subsequent breath, was created by two individuals who experienced a similar tragedy.  One is a pediatrician.

Hypothalamus and rebreathing

Subsequent studies focus on how deficits in the hypothalamus region of the brain can cause infants insufficient responses to carbon dioxide rebreathing

The brainstem and hypothalamus are two regions in which nuclei play an important role in stress responses and arousal mechanisms.

As deaths attributed to SIDS occur during sleep, failure to arouse in a stressful situation is a component of the proposed death mechanism. The hypothalamus is a small but complex part of the brain with important roles in the homeostasis of energy balance, circadian rhythms and stress responses, as well as growth and reproductive behavior. As a regulatory center for so many functions, it receives input and transmits output to various other brain regions.

Therefore, since the hypothalamus controls many physiological functions and is highly interconnected with other brain regions, it is an excellent candidate for abnormalities that contribute to the pathogenesis of SIDS.

The reduction of carbon dioxide remains a major concern for safe infant sleep, as it leads to:

  • Asphyxia
  • Hypercarbia
  • Hypoxia

Dangerous Advice on When Can a Baby Sleep on Their Stomach

Recommendations from medical professionals and popular pregnancy resources appear to have a common theme: Once your baby can roll over, they are safe to sleep on their stomach.

Community Baby Center, a credible baby forum sponsored by Johnson & Johnson, states, “If your baby is strong enough to roll from back to stomach and stomach to back alone, you don’t have to worry about him rolling and sleeping on his stomach”. In addition, Parents Magazine says, “If your baby can flip himself on his stomach while sleeping, it’s okay to leave him that way.”

Unfortunately, this is dangerous advice!

Current research

New Zealand researchers report: “Parents and caregivers are often concerned about the appropriate strategy for infants who have learned to roll over, which usually takes place at four to six months of age.  As infants mature, they are more likely to roll.  In a study, 6% and 12% of 16 to 23-week-old infants placed on their backs or sides were in the prone position; among infants aged 24 weeks or older, 14% of those placed on their backs and 18% of those placed on their sides in the prone position. 

Repositioning a sleeping infant to the supine (back) position can be disruptive.  Consequently, this could discourage the supine position. 

Data to produce specific recommendations as to when can a baby sleep on their stomach, is lacking.

Infants placed on their back who roll

Further, research shows  more than a quarter of infants who died of SIDS while sleeping on their tummy were last put on their back. These researchers suggest an infant’s ability to escape potentially lethal situations during stomach sleep may be impaired by inexperience in prone sleep.  Dr. Moon later supported their findings (Head of the AAP Safe Sleep Task Force) and colleagues in their review of infant sleep deaths in childcare centers.   

Unintended consequences

Unfortunately, infant inexperience with stomach sleep is now a common, unintended consequence of the successful back-to-sleep campaign.  Babies who roll and are not used to sleeping on their stomach are at greater risk of SIDS. 

According to researchers at Washington University School of Medicine in St. Louis, babies who never sleep on their stomachs do not learn behaviors that can reduce their risk of SIDS.  Consequently, the researchers warn infants should always be put on their backs to sleep.

In 2016, these same researchers recognized the safety benefits of air-permeable crib mattresses that do not allow carbon dioxide to accumulate on the mattress.

Babies who roll

“The first time babies who usually sleep on their backs or sides roll or are placed on their tummy have a 19-fold increase in the risk of sudden death,  We wonder if these babies, who find themselves face down, do not turn their heads to breathe because their reflexes haven’t developed far enough, or because they simply don’t wake up?” says SIDS researcher Bradley T. Thach, MD.

Additionally,  scientific studies indicate an ample head-lifting ability when lying on the stomach may not be sufficient to protect a baby from SIDS. “Many parents think if a baby can lift its head, it is okay to sleep on its tummy, but that is a false assurance,” Thach says. 

It’s starting to make sense why a crib mattress that eliminates the risk of an infant rebreathing their carbon dioxide is protective against SID!

About Dr. Thach

Dr. Brad Thach, now retired, spent most of his career as a SIDS researcher.  His research is still considered relevant.  He and Dr. James Kemp are credited with finding the link between rebreathing carbon dioxide and SIDS.

About Safe Sleep Policy Makers

Who are AAP policy-makers?  The Committee of the American Academy of Pediatrics (AAP) on Fetus and Newborn established the AAP Safe Sleep Task Force in the 1990s and currently monitors their work.  The members of the AAP Safe Sleep Task Force write the AAP Safe Sleep Policies and Guidelines.  The Task Force consists of five physicians who volunteer their time and expertise to make sense of the available data. Unfortunately, these scientists are not without their bias. 

For example, before the updated policy in 2016, a new doctor was added specializing in breastfeeding.  There is a new heightened awareness of the importance of breastfeeding to reduce the risk of SIDS.  Eventhoug, there are no gold standard scientific studies to support breastfeeding to prevent SIDS / SUID.

The AAP (including the Safe Sleep Task Force) does not endorse, certify or recommend certain products.  In addition, the AAP restricts interactions with manufacturers, making it difficult for manufacturers to ensure that their products are safe for consumers. 

Randomized Case Controlled Studies vs. Retrospective Analysis

AAP safe sleep policies are based on a retrospective analysis of infant deaths.  These investigations may be flawed.  Actual scientific tests are not carried out to prove SIDS theories, as unethical tests would be required.  Dr. James Kemp, who used baby bunnies, carried out the closest test showing rebreathing of carbon dioxide as a probable cause of SUID / SIDS. 

The AAP Safe Sleep Task Force use retrospective analyses to determine safe sleep recommendations.  Meaning, the best data they have is  filtering through thousands of infant death reports.  Next, they attempt to find correlations between infants in a particular age group, gender, weight, etc., to determine why some infants lived and others died.  Take, for example, the “back-to-sleep” recommendation.  These scientists found infants with similar profiles were more likely to die when they slept on their stomach than on their back.

Retrospective Analysis Can Be Flawed

Unfortunately, retrospective analysis data can be flawed and is subject to scientific interpretation.  SIDS death scene investigations are not currently standardized.  There are considerable efforts in this direction, but we are still not there.  It is up to the medical examiner or pathologist to determine the cause of death.  These individuals  take note of the series of events and the scene. 

However, some will be appropriate and complex in their findings and others will not.  Consequently, there is a high probability that one examiner will include data  that the other examiner will not.  Often examiners label a death as SIDS on the single fact the infant was sleeping during the incident.

Limitations of Safe Sleep Policy Makers

The absence of Randomized Case Controlled (Gold Standard) means recommendations are based on retrospective analyses.   For example, it is recommended not to use blankets for infants.  Instead, it is recommended to use wearable blankets.  There is no scientific study to conclude whether a wearable blanket prevents SIDS deaths. 

However, many death scene investigations show infants who died compared to infants in a similar environment who did not have loose blankets in their cribs.  This suggests loose blankets in the crib are an increased SIDS risk. 

The same applies to back sleep.  No gold standard scientific study has been carried out to show whether an infant is at increased risk of dying on his or her stomach. However, retrospective data shows infants who were on their back were much less likely to die during sleep, suggesting back sleep reduces the risk for SIDS.

Retrospective analysis suggests air-permeable sides and surfaces are preferable to air-impermeable sides and surfaces to protect against SIDS.  Science that dictates high air-permeability in crib mattresses is preferable.

SIDS and Crib Mattresses

Most of us know the importance of keeping fresh oxygen flowing to a sleeping baby.  Additionally, we now know the importance of avoiding anything in the crib that can block fresh oxygen or cause carbon dioxide to accumulate.  

Unfortunately, conventional crib mattresses with fiber fill, vinyl covers, quilted toppers, and loose sheets all impede fresh oxygen flow, Further, they cause causing carbon dioxide to accumulate.

According to Dr. James Kemp and Dr. Brad Thach, “These bedding materials prevent the dispersion of exhaled gases (carbon dioxide) and keep the gases near a face down infant’s mouth. With each subsequent breath, the infant takes in an air mixture gradually less appropriate to maintain life. The more conducive an object is to rebreathing (to preserve carbon dioxide), the more dangerous the object would be.”

SIDS experts agree infants sleeping on their  stomach on fiberfill crib mattresses, quilted surfaces, soft surfaces, pillow-like surfaces, vinyl pads, mattresses filled with tea tree bark and other natural fibers, and even surfaces that claim to be breathable, show an increased risk of rebreathing carbon dioxide.  

Imagine a crib mattress with no fill, no quilted topper, no need for sheets. A crib mattress with side opening and an open celled, firm topper that allows continuous air flow.

Safe Infant Sleeping in the Prone (Face-Down) Position

In the 2011 AAP Safe Sleep Policy and Technical Report, it states, “play yards and bassinets with vertical sides of air-permeable material may be preferable to those with air-impermeable sides.” The recommendation to include air-permeable sides in play yards and bassinets is based on retrospective studies by the AAP Chairperson of Task Force Safe Sleep, Dr. Rachel Moon and her colleague Dr. Jody Pike.

According to Moon and Pike, “We have carried out a retrospective review and analysis of deaths in bassinets between June 1990 and November 2004 reported to the CPSC.” Moon and Pike noted several infants who died were discovered with their faces near or pressed against the side of the bassinet or play yard that had no air-permeable sides.

In 2010, a pediatrician and her sister, a SIDS content expert,  began challenging members of the AAP Safe Sleep Task Force to include published studies confirming the safety benefits of air-permeable crib mattresses with no fill materials for infants who end up in a face-down position.  After all, they recommend air-permeable sides in bassinets and play yards.

Finally, in 2016, the AAP Safe Sleep Task Force states, “Crib mattresses were designed with air-permeable materials to reduce the rebreathing of expired gasses (carbon dioxide), in the event that an infant rolls to a prone position.  These crib mattresses may be preferable to those with air-impermeable materials.”

So, When Can A Baby Sleep on Their Stomach? 

After reviewing the following topics:

  • Why back sleeping is the best if your infant is sleeping on a traditional crib mattress with fiber fill or quilted surfaces.
  • We currently have no way to determine which infants who tummy sleep or roll over are at higher risk.
  • If your baby can roll over on their own from back to tummy and tummy to back, they are “safe” to tummy sleep – which is not only poor advice it could prove fatal.
  • Who our safe sleep policymakers are and the scientific limitations they face.
  • The issues with conventional crib mattresses that contribute to unsafe sleep conditions.
  • The safety benefits of air-permeability.

We can safely say there is no clear age or milestone to determine when it is safe for a baby to sleep on their stomach. However, there is an “air-permeable” alternative to conventional crib mattresses, recognized by AAP policymakers as preferable for infants who end up on their stomach while sleeping.

Air-permeable crib mattress

The test results of the SafeSleep® breathe-through crib mattress are included in the scientific studies reviewed by the AAP.  The SafeSleep® crib mattress is made of air-permeable materials and has no fill or core. Specifically, the design of the SafeSleep® air-permeable mattress eliminates the risk of rebreathing of expired gases (carbon dioxide) in the event that an infant is in a prone position during sleep.

SafeSleep ® does not have any fiber fill or core.  Instead, it has a hollow center with side openings and a firm, air-permeable topper to create an oxygen-rich environment.  

Scientific testing shows exhaled carbon dioxide is gone before a baby takes in their next breath, eliminating the risk of carbon dioxide rebreathing.

Best Crib Mattress
best crib mattress

Back sleep is safest, but if your baby insists on sleeping on his stomach, make sure he sleeps on an air-permeable crib mattress. If you want to learn more about the air-permeable crib mattress allowing an infant to breathe normally, even if face down, check out SafeSleep®’s fully breathe-through crib mattress.

We have no clear answer for when can a baby sleep on their stomach, but there is a clear answer for what a baby should sleep on if they are sleeping on their stomach!