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  • Post last modified:February 11, 2022

Sudden Infant Death Syndrome (SIDS) is a great worry for many parents. Learn about the risk factors and how to reduce them for your baby.

sudden infant death syndrome


What is Sudden Infant Death Syndrome?

Sudden Infant Death Syndrome or SIDS – sometimes called crib death or cot death – is the sudden and unexplained death of a seemingly healthy baby younger than one year old that usually happens during sleep.

Unfortunately, SIDS has no warning signs or symptoms.

Research can still not explain why a baby stops breathing and dies suddenly like this. Still, there are several theories and observations on variations between countries, gender, seasons, age, and more that may help you protect your child.

When using these metrics, if it seems that your baby may be at risk for SIDS, there are several precautionary steps you can take.

Read the article below and watch the video at the bottom of the article to learn about the risk factors and what protective measures you can take. Below the video, you’ll find the link to more information on how to create a safe sleeping environment for your baby.

Sudden Infant Death Syndrome Facts and Risk Factors

Unfortunately, SIDS remains mostly unexplained. Although we know what some of the main risk factors are and what to do to lower their impact or avoid them, for many factors, there is still no clear evidence to explain why exactly they are high risk (e.g., gender).

Physical Factors

Some babies are more likely to die of SIDS if, when they are born, the portion of their brain that controls breathing and arousal from sleep isn’t mature enough.

It has been shown that many infants who died of SIDS had had a cold in the weeks before death. Therefore, a respiratory infection may have contributed to the breathing problems.

Cultural Variations

SIDS happens in families of all social, economic, and ethnic groups. However, it has been shown that the incidence of SIDS varies depending on the country and ethnic groups. A high incidence has been noted in, for example, New Zealand, while Asia, the Netherlands, Sweden, and Finland have particularly few cases of Sudden Infant Death Syndrome.

Within the US, African American babies are twice as likely to die from SIDS than white babies, and American Indian babies are nearly three times more likely to die of SIDS than white babies.

The reasons for these differences are still not clear. However, it is suggested that several factors may play a role, such as behavioral, sociodemographic, and environmental.

It is important to note that the differences between countries have fallen since the general advice to let babies sleep on their backs was issued.

Gender and Age

Sudden Infant Death Syndrome is very uncommon for babies younger than one month. It is most common when babies are 2-4 four months old, which is also when the baby’s brain undergoes dramatic neurodevelopmental changes. After that period, the risk decreases. Only 20% of all cases occur when the baby is older than 6 months.

There are also gender differences in SIDS, with 60% of all affected babies being boys. As previously mentioned, SIDS is multi-factorial and probably happens as a combination of internal and environmental factors. Because of it, researchers still don’t have all the answers to why baby boys are more susceptible to SIDS than baby girls. One of the possible explanations may be found in the fact that baby boys have a higher risk of being born premature and a greater risk of suffering from conditions that are related to premature birth, such as respiratory distress syndrome.

Premature babies and babies with a low birth weight (less than 2500 gr, (5 pounds 8 ounces)) are also at higher risk of Sudden Infant Death Syndrome. Premature birth increases the likelihood that the baby’s brain didn’t mature completely. Because of it, premature babies may have less control over automatic processes, such as breathing.

Differences in time of the day, day of the week, and season

It has been shown that most babies who die of SIDS die at night and are found in the morning. However, SIDS death can occur during daytime sleeps also. According to some research, placing infants on their side to sleep was more observed amongst the daytime deaths.

SIDS is more common during weekends, but it is not clear why. Altered ways of living, such as that the parents consume more alcohol, is a possible explanation.

Somewhat more cases occur during winter. The general belief is that infections are more common during the colder months. In countries without these seasonal variations, Sudden Infant Death Syndrome appears to be higher during the semesters, supporting the theory that infections may cause SIDS. Another possible explanation is that babies are more likely to be overdressed or put under heavier blankets during winter, which may cause them to overheat or end up with their heads covered by the blanket.

Back to Sleep

Prone sleeping position (on the stomach) is a significant risk factor for SIDS, and it should be avoided.

It is unclear why placing the baby to sleep on their belly puts them at higher risk. However, there are several possible explanations, such as suffocation, the face-down position leading to oxygen deprivation which may result in hypoxia, rebreathing of carbon dioxide, reduced arousal response and increased waking thresholds, airway obstruction, and similar.

Babies who are placed on their side to sleep are also at a higher risk of SIDS. One of the possible reasons is that this way of sleeping makes it more likely that the baby will roll over on their belly during sleep.

Since the recommendation to put babies on their backs to sleep for all sleep times was issued, the percentage of infants placed on their backs to sleep has increased dramatically, and the rates of Sudden Infant Death Syndrome have declined by more than 50% in some countries.

Other Sleep Environmental Factors

Many studies showed that bed-sharing increases the risk of SIDS. Therefore, AAP strongly advises against it and emphasizes that the safest sleeping practice is to have the baby sleep in the parents’ bedroom, near the parents’ bed but on a separate surface designed for infants.

However, AAP recently adjusted its sleep guidelines, acknowledging the fact that bed-sharing still happens. Polls indicate that up to 70% of all parents bring their babies and older children in their family bed at least occasionally. If you put your baby in your bed to sleep, make sure to do it in the safest way possible by following safe co-sleeping guidelines.

Babies put to sleep on soft mattresses or couches, and similar are at higher risk for SIDS. According to some studies, babies who are placed to sleep on a soft surface have a five times higher risk of SIDS than those babies who sleep on a firm mattress.

Loose bedding also puts the baby at high risk, as they may land on top of the infant and make it difficult for them to breathe. AAP states that a large percentage of babies who die of SIDS are found with their head covered by bedding.

Overheating is another factor that increases the baby’s risk of SIDS. Research shows that when babies are overheated, they are more likely to go into a deep sleep from which it is hard for them to arouse.


The research is still unclear when it comes to the effects of swaddling on SIDS. Swaddling the baby may prevent them from rolling on their tummy, which may protect them from SIDS.

On the other hand, swaddling may put the baby at a higher risk for SIDS if the baby is swaddled after they are already able to roll over by themselves because it prevents them from lifting their head and moving if they are at risk of suffocation. Therefore, it is recommended that the parents stop swaddling the baby as soon as the baby shows any signs of trying to roll over.

Also, in the case of bed-sharing, swaddling is not recommended because it can lead to overheating, which is proven to increase the risk of SIDS.

Other Environmental Factors

The more children in a family, the higher the risk of Sudden Infant Death Syndrome. The reason for this is unknown but may have to do with either some factors during the pregnancy or the fact that the number of infections reaching the newborn baby increases with the number of children in the family.

If the baby is exposed to smoke in the womb or is later exposed to secondhand smoke, they have a higher risk of SIDS. According to some studies, babies whose mothers smoked during pregnancy are three times more likely to die of SIDS, and secondhand smoke doubles a baby’s risk for SIDS. It appears that the chemicals found in secondhand smoke affect the brain in ways that interfere with the brain’s regulation of an infant’s breathing.

Some research also showed that babies who died of SIDS had higher nicotine levels in their lungs and cotinine, which is a biological marker for secondhand smoke, than infants who died of other causes.

Babies whose mothers use drugs or alcohol are also at a greater risk of SIDS.

What is the difference between SIDS and SUID?

Sudden Unexpected Infant Death (SUID) is the sudden and unexpected death of a baby less than 1 year old in which the cause was not obvious before investigation. It is a broad term that encompasses all sudden infant deaths, including accidental deaths (such as suffocation and entrapment), sudden natural deaths (e.g., related to infection, ingestion, metabolic diseases, cardiac arrhythmias, etc.), trauma, or SIDS.

SIDS is one of several causes of SUID. However, unlike other causes of SUID, SIDS is given as a diagnosis only after all the other possible causes of sudden, unexplained death have been excluded (after a full investigation that includes an autopsy, death scene examination, and review of the clinical history).

Can a Baby Survive Sudden Infant Death Syndrome?

A common question to ask is whether a baby can survive SIDS. However, since SIDS is diagnosed only after death and by excluding other causes of death, it is not possibly to actually survive SIDS. So, even if the answer to this question may seem horrific, the reason for the no, is when SIDS is actually diagnosed (after death and after all other causes have been excluded).

How to Reduce the Risk of SIDS?

There are several important things you can do to lower the risk of SIDS.

As mentioned above, you should always place your baby on their back to sleep—for naps and at night. Once your baby is able to roll over both ways without help, you don’t have to place them on their back for sleep anymore, and you can let them choose their own sleeping position.

Place your baby to sleep on a firm mattress that maintains its shape. It is also essential that you never sleep with your baby on the armchair, couch, or sofa. These pose a great risk for the baby’s safety and significantly increase the risk of infant death, including SIDS and suffocation due to entrapment.

Keep the crib as bare as possible. Remove any loose bedding, bumpers, nursing pillows, stuffed animals, or any soft objects from your baby’s crib. Your baby’s crib needs only a tight-fitted sheet.

Keep your baby in your bedroom, near your bed, but place them to sleep on their own sleep surface, such as a crib or a bassinet. Research indicates that room-sharing without bed-sharing lowers the risk of SIDS by as much as 50%. However, if you decide to bed-share occasionally, follow the guidelines that teach you how to do it in the safest way possible.

Avoid overheating your baby by maintaining a comfortable temperature in a room where your baby is sleeping and by dressing them warm but not too warm. You can also consider using a sleep sack.

Don’t smoke during pregnancy, and avoid smoking around your baby. Also, make sure that no one else smokes around your baby.

Breastfeeding has been shown to lower the risk of SIDS by as much as 50%, so it is advisable to breastfeed as long as possible.

Consider using a pacifier because it has been shown that putting your baby to sleep with a pacifier may lower the risk of SIDS, although it is still not known why. However, it is recommended to wait until your baby is breastfeeding regularly (if you’re breastfeeding) before introducing the pacifier, so it doesn’t lead to nipple confusion. If your baby refuses a pacifier, don’t force it. If your baby falls asleep with a pacifier in their mouth but spits it out during sleeping, don’t put it back in their mouth while they are asleep.

It feels good to end this page on a positive note. I think it’s wonderful that something as simple as having your baby sleep on their back can make such a big difference in the risk of SIDS. Also, many doctors believe that the relatively new recommendation of using a pacifier is likely to lower the risk quite a lot further.

If you are truly worried about Sudden Infant Death Syndrome, there are very advanced baby monitors available. One of the best is Owlet’s baby monitor, with surveillance of a baby’s breathing and heart rate. (Opens in new window). It is very expensive, though, so you might want to check out other options too.However, if you deci de to use them, do thorough research on the product you’re buying. It is also important to mention that such devices sometimes give parents a misguided sense of security.

For more help on how to protect your baby from SIDS, read this article on how to provide a safe sleeping environment for your baby.

And if you are worried that your baby will, for example, get a flat head from all the back-sleeping – read this article about common worries that parents have when it comes to placing their babies on their backs to sleep, such as a flat head, choking and similar.


Video On Sudden Infant Death Syndrome

SIDS Awareness | Parents

Remember this to reduce the risk of Sudden Infant Death Syndrome :

  • Let your baby sleep on his back
  • Let him sleep on a firm mattress
  • Be careful with blankets and stuffed animals
  • Never smoke around your baby
  • Don’t smoke during pregnancy
  • Introduce a pacifier
  • Make sure your baby is not too warm while asleep
  • Breastfeed if possible


American Academy of Pediatrics. (2016). SIDS and other sleep-related infant deaths: Updated 2016 recommendations for a safe infant sleep environment. Pediatrics,138(5). https://doi.org/10.1542/peds.2016-2938

American SIDS Institute. (n.d.). What is SIDS/SUID? 

Blair, P. S., Ward Platt, M., Smith, I. J., Fleming, P. J. & the CESDI SUDI Research Group. (2006). Sudden Infant Death Syndrome and the time of death: factors associated with night-time and daytime deaths. International Journal of Epidemiology, 35(6), 1563-1569. https://doi.org/10.1093/ije/dyl212

Boston Children’s Hospital. (n.d.). Sudden Infant Death Syndrome (SIDS): Symptoms and causes.

Centers for Disease Control and Prevention. (n.d.). About SUID and SIDS. https://www.cdc.gov/sids/about/index.htm

Centers for Disease Control and Prevention. (n.d.). Health effects of secondhand smoke.

Duncan, J. R. & Byard, R. W. (2018). Sudden infant death syndrome: An overview. In J. R. Duncan & R. W. Byard (Eds.), SIDS Sudden Infant and Early Childhood Death: The Past, the Present and the Future. Adelaide (AU): University of Adelaide Press.

Healthy Children.org. (2020, August 17). Swaddling: Is it safe? https://www.healthychildren.org/English/ages-stages/baby/diapers-clothing/Pages/Swaddling-Is-it-Safe.aspx

Hobson, K. (2017, May 15). Racial and ethnic disparities persist in sudden infant deaths. NPR. https://www.npr.org/sections/health-shots/2017/05/15/528173372/racial-and-ethnic-disparities-persist-in-sudden-infant-deaths

Mayo Clinic. (n.d.). Sudden infant death syndrome (SIDS). https://www.mayoclinic.org/diseases-conditions/sudden-infant-death-syndrome/symptoms-causes/syc-20352800

New Parent Support. (2018, September). Swaddling a baby: the benefits, risks and seven safety tips.

Safe to Sleep. (n.d.). Common SIDS and SUID terms and definitions. https://safetosleep.nichd.nih.gov/safesleepbasics/SIDS/Common

Safe to Sleep. (n.d.). Research on other SIDS risk factors.

University of Southern California. (2008, March 25). Baby boys are more likely to die than baby girls. Science Daily. https://www.sciencedaily.com/releases/2008/03/080324173552.htm

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