Sudden Infant Death Syndrome (SIDS)

Sudden infant death syndrome (SIDS) is the sudden, unexplained death of an infant younger than 1 year old that remains unexplained after a complete investigation.

Overview

Sudden infant death syndrome (SIDS) is the leading cause of death in children between 1 month and 1 year of age. There is no sure way to prevent SIDS, but parents and caregivers can take steps to reduce the risk. The most effective action is placing a baby on their back to sleep for all naps and at night.

SIDS is one type of death within a broader category called sudden unexpected infant death (SUID). Sudden unexpected infant death includes other sleep-related deaths like suffocation, entrapment (when a baby gets trapped between two objects and cannot breathe), and strangulation (when something presses on or wraps around a baby’s neck, blocking the airway). These deaths are not SIDS.

Causes and Risk Factors

In most cases, infants appear healthy before a SIDS death occurs. No explanation for these deaths can be found, even after a complete postmortem examination. While there is no exact cause, there are many theories.

Research evidence suggests that infants who die from SIDS are born with brain abnormalities or defects. These defects are typically found within a network of nerve cells that rely on a chemical called serotonin, which allows one nerve cell to send a signal to another. These cells are located in the part of the brain that probably controls breathing, heart rate, blood pressure, temperature, and waking from sleep. Other research suggests that changes in the baby’s genes may cause problems with how the body functions, including breathing and waking from sleep.

Brain abnormalities and genetic factors may not be enough to cause a SIDS death. Evidence suggests that other events must also occur for an infant to die from SIDS. Researchers use the Triple-Risk Model to explain this concept.

The Triple-Risk Model

In this model, all three factors have to occur for an infant to die from SIDS. Having only one of these factors may not be enough to cause death from SIDS, but when all three combine, the chances of SIDS are high.

  • An at-risk infant. An infant has an unknown problem, such as a genetic change or a brain defect, that puts them at risk for SIDS. Healthcare providers, parents, and caregivers do not know about these problems.
  • An important time in the infant’s development. During the first 6 months after birth, infants go through many rapid phases of growth that can change how well the body regulates itself. Also, infants' bodies are learning how to respond to their environment.
  • Stressors in the environment. External stressors include being placed to sleep on the stomach, overheating during sleep, and exposure to cigarette smoke. An infant with an unknown problem and immature body systems may not be able to overcome these stressors.

Removing one of these factors, such as external stressors, may tip the balance in favor of the infant’s survival.

External Stressors

  • Sleep Position: Babies placed to sleep on their stomachs or sides are at higher risk for SIDS. Back sleeping carries the lowest risk for SIDS and is recommended.
  • Soft bedding: If an infant is placed to sleep on soft bedding, including blankets, pillows, sofas, and adult bed mattresses, the risk for SIDS increases.
  • Bed sharing: Infants who sleep in the same bed with their mother are at greater risk for SIDS and other kinds of sleep-related death. Bed sharing increases risk especially when the mother smokes, has recently consumed alcohol, is fatigued, or when the infant is covered by a blanket.
  • Smoking: Maternal smoking during pregnancy and smoke in the infant’s environment increase the risk of SIDS. Maternal cigarette smoking during pregnancy increases the risk of SIDS about threefold, independent of the baby’s birth weight.
  • Drug and alcohol use during pregnancy: Maternal drug and alcohol use during pregnancy increases the risk for SIDS.
  • Overheating: Over bundling or dressing baby in too many layers of clothing and bedding for the temperature of the room, can increase the risk of SIDS.

Other Known Risk Factors

  • Preterm birth: Infants born before 37 weeks in the womb are at higher risk for SIDS than infants born at full term.
  • Low birth weight:  Babies weighing 5 pounds, 8 ounces or less are at increased risk for SIDS.
  • Race and ethnicity: African American and American Indian/Alaska Native infants are at higher risk for SIDS than White, Hispanic American, or Asian/Pacific Islander American infants.

Prevention Guidance

Currently, there is no known way to prevent SIDS, but there are ways to reduce the risk. Many risk factors can be controlled or changed, but some cannot.

The American Academy of Pediatrics (AAP) Task Force on SIDS reviews all the latest scientific and clinical evidence about SIDS and other sleep-related infant deaths to make recommendations about the most effective ways to reduce risk.

It is important for all caregivers, parents, grandparents, aunts, uncles, babysitters, childcare providers, and everyone who might care for a baby to learn about safe infant sleep.

Safe Sleep Practices

  • Always place babies on their backs to sleep, for naps and at night.
  • Use a sleep surface that is firm (returns to its original shape quickly if pressed on), flat (like a table, not a hammock), and level (not at an angle or incline), covered only with a fitted sheet.
  • Keep all objects, toys, pillows, sheepskins, blankets, and crib bumpers out of the baby’s sleep area.
  • Use a wearable blanket to keep baby warm without loose blankets in the sleep area.
  • Make sure baby’s head and face stay uncovered during sleep.
  • Share a room with baby for at least the first 6 months, giving the baby their own sleep space, such as a crib, bassinet, or portable play yard, separate from your bed.

Feeding

  • Feeding babies human milk by direct breastfeeding, if possible, or by pumping, reduces the risk of SIDS.
  • Feeding only human milk, with no formula or other additions, for the first 6 months provides the greatest protection from SIDS.
  • Feeding human milk for some time is more protective against SIDS than not feeding human milk at all.

Smoke- and Substance-Free Environment

  • Stay smoke- and vape-free during pregnancy.
  • Keep baby’s surroundings smoke- and vape-free.
  • Make sure anyone caring for baby is drug- and alcohol-free.

Other Protective Actions

  • Offer baby a pacifier for naps and at night once they are breastfeeding well. Several studies have shown that infants who use pacifiers are at decreased risk of SIDS.
  • Avoid letting baby get too hot.
  • Get regular medical care throughout pregnancy.
  • Follow healthcare provider advice on vaccines, checkups, and other health issues for baby.
  • Give babies plenty of “tummy time” when they are awake and someone is watching them.
  • Avoid swaddling once baby starts to roll over, usually around 3 months of age. Swaddling does not reduce SIDS risk.

Products to Avoid

Some products claim to prevent SIDS or safely position an infant for sleep. These products may include wedges, positioners, special mattresses, and special sleep surfaces. The U.S. Consumer Product Safety Commission, the Food and Drug Administration, and the American Academy of Pediatrics warn against using these products because of the dangers they pose to infants and because there is no evidence that they reduce SIDS.

Some breathing and heart monitors claim to be able to detect SIDS before it happens. These products might be prescribed by healthcare providers to manage certain medical conditions, but research shows that these monitors are not effective at detecting SIDS or reducing SIDS risk.

Research shows that crib bumper pads or padded bassinets can cause injury or death to infants. Evidence does not support using crib bumpers to prevent injuries, and evidence shows that crib bumpers can cause serious injuries and death.

Back Sleeping and Choking

Some parents worry that placing a baby on their back to sleep may cause choking. Healthy infants naturally swallow or cough up fluids; it is a reflex all people have. When a baby is in the back sleep position, the windpipe lies on top of the esophagus, so anything regurgitated has to work against gravity to enter the trachea. When a baby sleeps on their stomach, such fluids pool at the opening of the trachea, making choking much more likely. The number of fatal choking deaths has not increased since back sleeping recommendations began.

Flat Head Spots

Back sleeping may increase the risk of flat spots on the head, a condition called positional plagiocephaly. However, flat spots are much less serious than SIDS and can often be prevented and treated. Parents should not stop placing infants on their backs to sleep but should offer tummy time while the baby is awake and change the direction the baby lies in the crib to encourage more head movement. If you have concerns about the shape of your infant’s head, talk with your child’s healthcare provider.

Diagnosis

SIDS is diagnosed by a process of elimination. A diagnosis requires a complete investigation that can include:

  • An autopsy
  • A review of the death scene
  • A review of complete family and medical histories
  • Collecting information and conducting scientific or forensic tests
  • Talking with parents, caregivers, and healthcare providers

If, after this process is complete, there is still no identifiable cause of death, the infant’s death may be labeled as SIDS.

Living With Loss

One of the most important things to remember when an infant dies from SIDS is that the families themselves are not to blame. The causes of SIDS remain unknown, and even though there are ways to reduce the risk, there is no definitive way to prevent SIDS from occurring.

Talking to other parents or caregivers who have lost an infant to SIDS may also be helpful. A healthcare provider may be able to recommend local resources and groups.

Find Clinical Trials

Clinical trials uncover better ways to prevent, diagnose, treat, and understand diseases and conditions. To ensure results apply to everyone, volunteers of all ages, sexes, and backgrounds, including both healthy individuals and those with specific medical conditions, are needed. Find clinical trials on sudden infant death syndrome.

Community Support

Note: This resource list is for informational purposes only. It is not comprehensive, and an organization’s inclusion does not constitute an endorsement by NIH. 

Research Information

The National Institutes of Health (NIH) is the largest public funder of biomedical research in the world. NIH invests most of its budget in medical research seeking to enhance life and to reduce illness and disability. NIH-funded research has led to breakthroughs and new treatments helping people live longer, healthier lives, and building the research foundation that drives discovery.

The National Institutes of Health (NIH) supports research on the causes and biology of SIDS, research on risk factors, especially among certain portions of the U.S. population, and outreach designed to educate parents and caregivers about ways to reduce SIDS risk.

NIH’s research goals include four key areas:

  • Etiology and pathogenesis. Understanding how neural abnormalities in SIDS infants develop and how they affect health before and after birth, including whether genetic factors may predispose infants to SIDS.
  • Prognostics and diagnostics. Examining the effectiveness of tools to assess neurological and developmental maturation from fetal life through early infancy and of screening tools used in the neonatal period.
  • Preventive strategies. Leading studies and sponsoring activities to raise awareness of SIDS and how to reduce the risk, with an emphasis on strong community partnerships.
  • Health disparities. Focusing on community resources and investigating both protective and adverse forces at work within populations to reduce the risk and incidence of SIDS.

Key Research Findings

  • Brain abnormalities of SIDS infants may underlie processes that may lead to SIDS. Almost 20 years of NIH-supported research led to the finding of a deficit in the neural network within the medullary raphe of the brainstem that is unique to SIDS infants. This network uses the neurotransmitter serotonin and controls heart rate, breathing, blood pressure, temperature, and arousal from sleep. Three-fourths of SIDS infants in one study had brainstem abnormalities. Ongoing studies on the medullary deficiency seek to understand the underlying basis of the deficiency and how this affects infants’ inability to resuscitate themselves following life-threatening challenges such as hypoxia.
  • Infant sleep practices and external factors impact SIDS risk. Ongoing studies on sleep position focus on the decreased arousal response in stomach sleepers compared with infants who sleep on their backs. NICHD researchers are also studying sleep position decisions and other factors that influence SIDS risk. The goal of these efforts is to improve the design, implementation, and effectiveness of risk reduction strategies for SIDS and causes of infant death associated with the sleep environment.
  • Advice to avoid bedsharing does not discourage breastfeeding. NIH-funded researchers found that more than half of women who exclusively breastfed were following guidelines on sharing the sleeping room with their infants rather than sleeping with the baby. Infants who sleep in the same bed as parents, siblings, or pets are at greater risk of SIDS.
  • Genetics may contribute to SIDS risk. NICHD researchers identified a mutation in 5%–10% of SIDS infants. The mutations were in a cardiac sodium-channel gene and have been found in congenital heart conditions and arrhythmia, which can lead to cardiac arrest. Recent studies have found rare mutations in several other genes that control cardiac rhythm that may be a potential cause of or contributor to some cases of SIDS. Known genetic disorders of metabolism likely account for up to 5% of SIDS cases.

The Safe to Sleep® Campaign

The Safe to Sleep® Campaign (formerly Back to Sleep) was developed to raise awareness about and to educate parents, caregivers, and healthcare providers on ways to reduce the risk of SIDS and other sleep-related causes of infant death. Recommendations in the campaign materials are based on the AAP Task Force on SIDS recommendations. Since NIH and its collaborators launched the campaign in 1994, the U.S. SIDS rate has declined by more than 50%, and the percentage of infants placed on their backs to sleep has more than tripled.

Find NIH-funded research projects using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies.  

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