What You Need to Know About Sudden Infant Death Syndrome (SIDS) and Sleep

Table of Contents

Recommendations around safe sleep can inflame the passionate opinions of just about any parent or parent-to-be. Discussion boards and baby showers can turn into heated debates between the bed-sharer and bassinet crowd, the breastfeeders and bottle-feeders, and any other number of divisions in parenting choices. No one likes to think about the possibility of sudden infant death, much less talk about it. Luckily, the American Academy of Pediatrics (AAP) regularly updates its guidelines — let’s take a look at what current research says. (1) (2)

Long Story Short

  • SIDS (sudden infant death syndrome) describes the unexplained death of an otherwise healthy baby less than 12 months old.
  • No one knows the exact cause of SIDS, but risk factors can include age, birth weight, exposure to nicotine and alcohol during pregnancy, co-sleeping, and sleeping on the tummy or on a soft surface.
  • You can lower the risk for SIDS by addressing as many risk factors as possible. Sharing a room (not a bed), tummy time, breastfeeding, and pacifiers can also lower SIDS risk.

What is SIDS? 

“SIDS (sudden infant death syndrome) is the unexplained death of a seemingly healthy infant under 12 months old, typically occurring while the child is sleeping,” Dr. Harvey Karp, American Academy of Pediatrics fellow and SIDS/SUID expert, tells Sleepopolis.

Though the term “SIDS” is largely considered outdated, many healthcare providers — and parents — still use it. The terminology for sudden infant death has gone through different iterations over the years but has now been updated to “unexplained sudden death in infancy,” which is a subcategory of SUID: sudden unexpected infant death. (3) Here’s how it breaks down:

  • Sudden unexpected infant death (SUID) is any sudden and unexpected death (explained or unexplained) during infancy.
  • Unexplained sudden death in infancy (previously known as SIDS) is a subcategory of SUID and is used to describe any sudden infant death that cannot be explained, even after an autopsy.

That being said, most people still call it SIDS, so parents shouldn’t worry about using the new terms.

What Causes SIDS?

No one knows exactly what causes SIDS, says Karp, but many factors can play a part in sudden infant death, including brain chemistry abnormalities and genetic mutations. “Today, we recognize that SIDS makes up just a portion of infant sleep deaths,” Karp says. “In fact, many [deaths] that used to be attributed to SIDS were actually caused by accidental suffocation when the baby’s nose and mouth were covered by the mattress or bedding.”

Research has uncovered some common triggers for unexplained infant death. “The underlying cause of SIDS is multifactorial,” Dr. Lauren Beene, pediatrician and clinical instructor of pediatrics for Case Western Reserve University, tells Sleepopolis. Even though it’s not fully understood, she says evidence supports that a specific combination of risk factors can play a role.

SIDS Risk Factors

If you’re starting to feel panicky, stick with us a little longer — this is a tough subject. But once you know the risk factors for SIDS, you can address them. Infants may be at the highest risk for a sudden death event when all three of the following risks apply: (2)

  • Intrinsic vulnerability: premies or babies with chronic medical conditions
  • Exogenous trigger: something in the baby’s environment, like loose blankets in the crib
  • Critical developmental period: like the 4-month regression or learning to crawl

“SIDS is associated with a number of risk factors, many of which are avoidable,” says Beene. “In more than 95 percent of SIDS cases, one or more risk factors was involved.” Some of these factors, like age and birth weight, cannot be helped. But you can adjust others to lower your baby’s risk. First, let’s look at the risk factors themselves.


Before a baby reaches one month old, their risk of SIDS is almost zero, but risk peaks for infants around two and three months old. About 90 percent of SIDS cases occur before six months of age, and the remaining 10 percent happen before the one-year mark. (4)

Low Birth Weight 

Sometimes babies come out tiny, which may increase SIDS risk in some cases. To be small enough for the risk to apply, birth weight has to be five pounds, eight ounces or less. (5)

Sibling SIDS Event

If the older sibling of an infant had a sudden death event, they may be up to four times more likely to experience a SIDS event. Experts think this could be because of similar environmental surroundings and genetics. (6)


Your grandma may scold you for “letting that baby freeze,” but it’s actually much safer to keep your baby cool. (2) When babies overheat, they can experience something called thermal stress, which makes it harder for them to wake up and increases their SIDS risk. (7)

What room temperature is right for babies?

Temperature recommendations can vary, but as a rule of thumb, look at what you’re wearing to be comfortable, and add no more than one layer to your baby. For example, if you’re comfy in shorts and a t-shirt, don’t put your baby in thick fleece pajamas and a jacket. After the adorable first few days of hat-wearing, keep that cue-ball naked when inside. Not sure if they’re too hot? Keep an eye out for signs of overheating like sweating, flushed skin, or the chest feeling very hot to the touch. (2)

Co-Sleeping (Sharing Bed with Parents)

So many parents love bed-sharing, and this risk factor can be a difficult one to read. But the latest evidence tells us that babies who sleep in a bed, on a couch, or in an armchair alone or with a loved one or pet are at a very high risk for SIDS. The fluffy fabric and stuffing that make these places so comfortable for adults and older children can be dangerous for infants because of the possibility of cutting off or blocking their air supply. (5)

Poor Prenatal Care 

Driving to your OBGYN or other prenatal healthcare provider on the reg is one of the hassles of pregnancy. But this care leading up to the big day is extremely important for your baby’s health before and after birth, and may even lower the risk of SIDS. (5)

Side or Stomach Sleeping

This is another one grandma may fight you on, but babies younger than three or four months can’t always roll over on their own. So if they fall asleep on their stomach or their side and roll onto their tummy, they may not be able to roll back over or move their face to get good breaths. (5)

Sleeping on a Soft Surface 

Sounds nice, right? Well, it is for us creaky over-30-year-olds, but babies don’t notice the difference very much. And while soft surfaces may seem to cradle that baby just right, the plush stuffing can cover their mouth and nose and prevent breathing. (5)

Sleeping on an Incline

It can be incredibly tempting to leave your baby in their car seat after they fall asleep on a long drive. And you may feel that sleeping in their swing is the only way your baby (or you) will get any rest at all. But the AAP says that any incline over 10 percent can increase the risk for SIDS. (2)

Maternal Tobacco or Alcohol Use

Tobacco and alcohol aren’t great for your health in general (8), but smoking and drinking alcohol during pregnancy can also put your baby at a higher risk for sudden infant death after birth. In one large study review, smoking during pregnancy doubled the risk of SUID in the first year. (9)

The research isn’t quite clear on how connected alcohol use during pregnancy is with SIDS after birth, but several recent studies have shown that alcohol consumption along with smoking beyond the first trimester during pregnancy can lead to a much higher risk of SIDS. (10)


Health disparities can affect people of all ages, including infants. As SIDS rates have decreased across the country, non-Hispanic Black and American Indian/Alaska Native communities have seen a slower decline. The AAP tells us that these communities in the United States are more likely to experience disadvantages in socioeconomic status and have more SIDS risk factors. (2)


In their 2022 sleep recommendation update, the AAP recommended breastfeeding to reduce SIDS risk. (2) Breastfed infants two to three months old can be woken up more easily than formula-fed infants. Breast milk also protects your baby by boosting immunity and promoting brain development. (11)

Of course, how you feed your baby is a very personal decision, and we know it isn’t always as simple as what you may prefer. Know that whether you choose to breastfeed or formula-feed, you can still take steps to reduce the risk of SIDS.

Other Risk Factors

Health information can be tricky to navigate as a new parent. One website says one thing, your neighbor says another, and your auntie disagrees with them both. Who should you listen to? 

A growing group of people are concerned about the connection between infant vaccination and SIDS. The health community has heard this concern and has performed many, many studies to suss out the truth. According to the Centers for Disease Control, none of these studies have shown any connection between infant vaccines and SIDS. (12)

Some research has suggested that poor ventilation and air pollution can increase SIDS risk, and some small studies have shown a decreased risk when a fan is on in the baby’s room while they sleep. (13) These results are valid, but more studies need to be done to prove this is true. (1)

SIDS Trends

Currently, 3,500 infants die each year from sudden unexpected deaths in the U.S. “In the early 1990s, doctors launched a ‘Back to Sleep’ campaign based on the observation that back sleeping substantially reduced the risk of SIDS/SUID,” says Karp. “Within just 5 years, these deaths were reduced by almost 50 percent.” Since 2000, that plunge leveled off until 2020, when there was a small increase. (2) (14)

In 2020, the U.S. hit a record low in overall infant deaths, but SIDS cases increased from 2019 to 2020, and experts have tried to find out why. The AAP believes the uptick could have been caused by the COVID pandemic but also could stem from a change in the way providers and investigators label the cause of death in these cases. (15)

When Does the Risk for SIDS Decrease?

It’s always nice to know when you can check one thing off of your long list of worries as a parent. SIDS risk is just about zero after the first year. At that point, babies are extremely mobile and able to do all kinds of gymnastics in bed to get into a good position for breathing. (16)

Even after six months, the risk goes down by a lot. Ninety percent of SIDS deaths happen before babies reach six months of age. Babies one to four months old account for 72 percent of all cases. (17) Basically, the older they get, the less you need to worry. 

Reducing the Risk of SIDS

Another way to combat SIDS anxiety is to reduce some of those risk factors. “Today we know that back sleeping is the only safe sleeping position for babies, and it’s the number one safe sleep recommendation by all public health authorities,” says Karp. “According to the National Institutes of Health, back sleeping is ‘the single most effective action that parents and caregivers can take to lower a baby’s risk of SIDS,’” he adds. (2

If you’re a new parent, it will probably feel strange to place your sleepy angel onto a bleak, empty, seemingly rock-hard mattress. But have no fear! Your baby is so light, they will feel perfectly comfortable. They also won’t notice the absence of fluffy blankets or stuffed animal friends.

Beyond setting up a safe sleeping space, here are some other ways you can reduce your baby’s risk of SIDS: (2) (17)

  • After breastfeeding is established, encourage baby to use a pacifier
  • After the swaddling stage, you can try non-weighted wearable blankets
  • Avoid soft bedding or over-bundling (this includes plush crib guards)
  • Breastfeed if possible
  • Keep any loose toys or stuffed animals out of the crib
  • Keep baby up-to-date on immunizations
  • Make sure their crib is sturdy and put together correctly
  • No hats inside (except in the NICU or right after birth)
  • Once baby starts to try and roll over, stop swaddling
  • Put baby on their back to sleep (14)
  • Use a firm, flat sleep surface 
  • While pregnant, avoid exposure to nicotine, alcohol, marijuana, opioids, or illicit drugs

These tips were approved by the AAP in 2016, but in 2022 they added a few more. (2) The AAP now recommends parents share a room (but not a bed) with their newborn for at least six months. They also suggest twins and any other multiples sleep in separate bassinets or cribs

You can also help your baby stay safe by encouraging them to “work out” their neck and back muscles. Daily tummy time, with the goal of 15 to 30 minutes a day by 7 weeks old, can help strengthen your baby so they can move to get a good breath while they sleep. (2)

Your baby probably won’t like tummy time, but it’s essential to their development and safety! As long as you’re there with them, cheering them on, they’ll be safe during tummy time. At first, they’ll faceplant a lot, but soon enough they’ll be able to hold their head up for longer periods and be less cranky about it. (2)

Some people swear by home-monitoring devices that track heart rate and oxygen levels. While these monitors might give parents some peace of mind, they can also make them complacent in applying the guidelines above. For example, they may bundle their baby up with a cozy, loose blanket because they feel the monitor will tell them if there is a problem. Feel free to use these devices, but apply all the safe sleep tips above.

The Last Word From Sleepopolis 

Ultimately, if you feel strongly about this topic, it is because you feel strongly about giving your child the best life imaginable. These guidelines are based on years of evidence and study, and the AAP encourages all parents and caregivers to become familiar with them and to allow their baby the safest sleep possible.


What are the warning signs of SIDS?

Unfortunately, the answer to this is none. “There are no warning signs or symptoms of SIDS,” says Dr. Beene. “This is why it is so important to avoid risk factors and ensure an infant has a safe sleep environment before being put to bed.” (18) You can follow the safe sleep tips above to decrease your baby’s risk.

Is using a baby monitor while my newborn sleeps in a different room as safe as room sharing?

Baby monitors are never a substitute for direct supervision,” cautions Karp. “There’s no evidence that using a baby monitor decreases the chance of SIDS. On the other hand, room sharing has been shown to reduce the risk of SIDS by as much as 50 percent. For this reason, pediatricians recommend infants sleep in their parents’ room — in a crib or bassinet — for at least the first 6 months.” (2)

How do I know if my crib is safe?

“You can check to make sure your crib hasn’t been recalled at cspc.gov/recalls. But you can also rest easy knowing that because of baby crib safety standards in America, if you bought a new crib and new mattress that fits the crib, and you followed the directions to put the crib together, your crib is safe.” says Karp. (19)

Why does a pacifier help prevent SIDS?

“We actually don’t know why exactly sucking on a pacifier helps to reduce the risk of SIDS,” says Dr. Karp, but he adds that research has shown that babies who go to sleep with pacifiers have a lower risk for a sudden death event. The AAP agrees pacifier use can decrease the risk for SIDS and recommends parents offer one as soon as breastfeeding is up and running. (2)

Why is stomach sleeping dangerous?

“Stomach sleeping is thought to obstruct a baby’s airway and interfere with their body’s ability to distribute heat, which can lead to overheating…another SIDS risk factor,” says Dr. Karp. “It’s also believed that babies who sleep on their tummies may be ‘rebreathing’ their own exhaled breath…leading to a rise in carbon dioxide and a drop in oxygen.” (2


  1. Moon RY, Carlin RF, Hand I, THE TASK FORCE ON SUDDEN INFANT DEATH SYNDROME and THE COMMITTEE ON FETUS AND NEWBORN. Evidence Base for 2022 Updated Recommendations for a Safe Infant Sleeping Environment to Reduce the Risk of Sleep-Related Infant Deaths. Pediatrics. 2022;150(1):e2022057991. doi:10.1542/peds.2022-057991
  2. Moon RY, Carlin RF, Hand I, THE TASK FORCE ON SUDDEN INFANT DEATH SYNDROME AND THE COMMITTEE ON FETUS AND NEWBORN. Sleep-Related Infant Deaths: Updated 2022 Recommendations for Reducing Infant Deaths in the Sleep Environment. Pediatrics. 2022;150(1):e2022057990. doi:10.1542/peds.2022-057990
  3. Shapiro-Mendoza CK, Palusci VJ, Hoffman B, et al. Half Century Since SIDS: A Reappraisal of Terminology. Pediatrics. 2021;148(4):e2021053746. doi:10.1542/peds.2021-053746
  4. Allen K, Anderson TM, Chajewska U, Ramirez J, Mitchell EA. Factors associated with age of death in sudden unexpected infant death. Acta Paediatrica. 2021;110(1):174-183. doi:10.1111/apa.15308
  5. What Are the Known Risk Factors? | Safe to Sleep®. Accessed September 23, 2024. https://safetosleep.nichd.nih.gov/about/risk-factors
  6. Glinge C, Rossetti S, Oestergaard LB, et al. Risk of Sudden Infant Death Syndrome Among Siblings of Children Who Died of Sudden Infant Death Syndrome in Denmark. JAMA Netw Open. 2024;6(1):e2252724. doi:10.1001/jamanetworkopen.2022.52724
  7. Bach V, Libert JP. Hyperthermia and Heat Stress as Risk Factors for Sudden Infant Death Syndrome: A Narrative Review. Front Pediatr. 2022;10:816136. doi:10.3389/fped.2022.816136
  8. Ohlrogge AH, Frost L, Schnabel RB. Harmful Impact of Tobacco Smoking and Alcohol Consumption on the Atrial Myocardium. Cells. 2022;11(16):2576. doi:10.3390/cells11162576
  9. Anderson TM, Lavista Ferres JM, Ren SY, et al. Maternal Smoking Before and During Pregnancy and the Risk of Sudden Unexpected Infant Death. Pediatrics. 2019;143(4):e20183325. doi:10.1542/peds.2018-3325
  10. Elliott AJ, Kinney HC, Haynes RL, et al. Concurrent prenatal drinking and smoking increases risk for SIDS: Safe Passage Study report. EClinicalMedicine. 2020;19:100247. doi:10.1016/j.eclinm.2019.100247
  11. Meek JY, Noble L, Section on  Breastfeeding. Policy Statement: Breastfeeding and the Use of Human Milk. Pediatrics. 2022;150(1):e2022057988. doi:10.1542/peds.2022-057988 https://www.federalregister.gov/documents/2020/01/31/2020-01832/review-of-the-safety-standards-for-full-size-baby-cribs-and-non-full-size-baby-cribs
  12. SIDS and Vaccines | Vaccine Safety | CDC. Accessed September 24, 2024. https://www.cdc.gov/vaccinesafety/concerns/sids.html
  13. Hwang MJ, Cheong HK, Kim JH. Ambient Air Pollution and Sudden Infant Death Syndrome in Korea: A Time-Stratified Case-Crossover Study. IJERPH. 2019;16(18):3273. doi:10.3390/ijerph16183273
  14. Campaign History | Safe to Sleep®. Accessed September 24, 2024. https://safetosleep.nichd.nih.gov/campaign/history
  15. Shapiro-Mendoza CK, Woodworth KR, Cottengim CR, et al. Sudden Unexpected Infant Deaths: 2015–2020. Pediatrics. 2024;151(4):e2022058820. doi:10.1542/peds.2022-058820
  16. SIDS by Baby’s Age Infographic (Text Alternative) | Safe to Sleep®. Accessed September 24, 2024. https://safetosleep.nichd.nih.gov/resources/social-digital/sids-by-babys-age-infographic-text-alternative
  17. Safe Sleep Environment | Safe to Sleep®. Accessed September 24, 2024. https://safetosleep.nichd.nih.gov/reduce-risk/safe-sleep-environment
  18. Sudden infant death syndrome: MedlinePlus Medical Encyclopedia. Accessed September 24, 2024. https://medlineplus.gov/ency/article/001566.htm
  19. Federal Register :: Review of the Safety Standards for Full-Size Baby Cribs and Non-Full-Size Baby Cribs. Accessed September 24, 2024. https://www.federalregister.gov/documents/2020/01/31/2020-01832/review-of-the-safety-standards-for-full-size-baby-cribs-and-non-full-size-baby-cribs
  20. Karp, Harvey, MD. Personal Interview. September 22, 2024.
  21. Beene, Lauren, MD. Personal Interview. September 22, 2024.
Abby McCoy

Abby McCoy

Abby McCoy is an RN of 16 years who has worked with adults and pediatric patients encompassing trauma, orthopedics, home care, transplant, and case management. She has practiced nursing all over the world from San Fransisco, CA to Tharaka, Kenya. Abby loves spending time with her husband, four kids, and their cat named Cat.