Monday, May 27, 2024
Homebreast cancerSudden Infant Death Syndrome (SIDS) Causes, Prevention & Facts

Sudden Infant Death Syndrome (SIDS) Causes, Prevention & Facts

Sudden infant death syndrome (SIDS) facts

  • Sudden infant death syndrome is the sudden, unexpected death of an infant younger than 1 year of age.
  • It typically occurs associated with a period of sleep.
  • SIDS is rare during the first month of life. Risk peaks in infants 2-4 months of age and then declines.
  • Medical professionals diagnose SIDS once all recognizable causes of infant death have been ruled out, including infection, trauma, or a condition related to the heart, lungs, or central nervous system.
  • People can reduce a child's SIDS risk by following the guidelines of the "Safe to Sleep" campaign, including placing an infant to sleep on his/her back and avoiding objects within the sleep space that may interfere with normal breathing.

What is sudden infant death syndrome (SIDS)?

Approximately 3,500 infants die suddenly and unexpectedly each year in the United States. Sudden unexpected infant death (SUID) include sudden infant death syndrome (also known as SIDS), accidental suffocation in a sleeping environment, and other deaths from unknown causes. Sudden infant death syndrome (also known as SIDS) is the sudden, unexpected death of an infant younger than 1 year of age. If the child's death remains unexplained after a formal investigation into the circumstances of the death (including performance of a complete autopsy, examination of the death scene, and review of the clinical history), the death is then attributed to SUID or SIDS. Sudden infant death is a tragic event for any parent or caregiver.

  • Medical professionals suspect SIDS when a previously healthy infant, usually younger than 6 months of age, is found dead following a period of sleep. In most cases, no sign of distress is identifiable. The baby typically feeds normally prior to going to sleep. A caregiver then discovers the infant lifeless, without pulse or respiration. Cardiopulmonary resuscitation (CPR) may be initiated at the scene, but evidence shows a lack of beneficial effect from CPR. The cause of death remains unknown despite a careful review of the medical history, scene investigation to exclude sleep-associated factors, and an autopsy.
    • SIDS is rare during the first month of life. Risk peaks in infants 2-4 months of age and then declines.
    • About 90% of SIDS deaths occur in infants younger than 6 months of age.

SIDS Prevention

While SIDS isn’t completely preventable, parents can take measures to reduce their infant’s risk of SIDS:

  • The American Academy of Pediatrics recommends that all healthy infants under one year of age be placed on their backs to sleep. Remember the slogan “back to sleep.”
  • If you smoke, stop smoking before pregnancy and do not allow your baby to be exposed to passive smoke.
  • Sleeping in a crib in a parent’s room is safer in terms of SIDS risk than sharing a bed with adults or sleeping in a room alone.

Learn more about SIDS risk factors and prevention »

What is the cause of SIDS?

The cause (or causes) of SIDS is still unknown. Despite the dramatic decrease in the occurrence of SIDS in the United States and worldwide in recent years, SIDS remains one of the leading causes of death during infancy beyond the first 30 days following birth. SIDS may be the result of multiple interacting factors.

  • Infant development: A leading hypothesis is that SIDS may reflect a delay or abnormality in the development of nerve cells within the brain that are critical to normal heart and lung function. Research examinations of the brainstems of infants who died with a diagnosis of SIDS have revealed a developmental delay in the formation and function of several serotonin-binding nerve cell pathways within the brain. These pathways are crucial to regulating breathing, heart rate, and blood pressure responses during awakening from sleep.
    • The hypothesis is that certain infants, for reasons yet to be determined, may experience abnormal or delayed development of specific critical areas of their brain. This could negatively affect the function and connectivity to regions regulating arousal during sleep.
    • Arousal, in this context, refers to an infant's ability to awaken and/or respond to a variety of physiological stimuli. For example, a child sleeping facedown (prone) may move his or her face into such a position so that the nose and mouth are completely obstructed. This may alter the levels of oxygen or carbon dioxide in the infant's blood. Normally, these changes would trigger arousal responses, prompting the infant to move his or her head to the side to relieve this obstruction.
    • Other protective responses to stressful stimuli may be defective in infants who are vulnerable to SIDS. One such reflex is the laryngeal chemoreflex, which arises from nerve cell pathways located in the back of the throat (pharynx) and within the voice box (larynx) and upper airway. This reflex regulates changes in breathing, heart rate, and blood pressure when fluids like saliva or regurgitated stomach contents stimulate portions of the airway. Having saliva in the airway may activate this reflex, triggering swallowing responses that help to keep the airway clear. When an infant is in the facedown position, the rate of swallowing decreases. Protective arousal responses to these laryngeal reflexes also diminishes in active sleep when infants are in the facedown sleep position.
  • Rebreathing stresses: When a baby is facedown, air movement around the mouth may be impaired. This can cause the baby to re-breathe carbon dioxide that the baby has just exhaled. Soft bedding and gas-trapping objects, such as blankets, comforters, waterbeds, sofas, chairs, and soft mattresses, as well as stuffed or plush toys are other types of sleep surfaces that may impair normal air movement around the baby's mouth and nose when positioned facedown.
  • Hyperthermia (increased temperature): Overdressing, using excessive coverings, or increasing the air temperature may lead to an increased metabolic rate in these infants and eventual loss of breathing control. However, it is unclear whether the increased temperature is an independent factor or if it is just a reflection of the use of more clothing or blankets that may act as objects obstructing the airway.

Even though the specific cause (or causes) of SIDS remains unknown, scientific efforts have eliminated several previously held theories. We now know the following about SIDS:

  • Apnea is a term that describes the clinical situation in which a person's breathing stops spontaneously. Apnea associated with prematurity and apnea that occurs during infancy are felt to be clinical conditions that are distinct from SIDS. Electronic monitors prescribed by doctors that track heart rate and respiratory activity may manage infants with apnea in some cases. Apnea monitors will not prevent SIDS.
  • SIDS is neither predictable nor preventable.
  • Infants may experience episodes termed brief, resolved unresponsive episodes (BRUE: previously called apparent life-threatening events or ALTE). These are clinical events in which young infants may experience abrupt changes in breathing, color, or muscle tone. Common causes of BRUE include viral respiratory infection (RSV), gastroesophageal reflux disease, or seizure. However, no definite scientific evidence links BRUEs as events that will lead to SIDS.
  • Immunizations and bad parenting do not cause SIDS.
  • SIDS is not contagious or hereditary.
  • SIDS is not anyone's fault.


Newborn babies don’t sleep very much.
See Answer

What are the risk factors for SIDS?

Research studies continue to demonstrate a greater risk for SIDS among male infants. SIDS occurs more frequently during winter months than summer months, although this distribution is not as pronounced in recent years as it had been in the past. In the United States, both African-American and Native-American infants have a higher rate of SIDS than do Caucasian, Hispanic, and Asian infants.

Certain infant care practices have an effect on the risk for SIDS. Most notable is the increased risk associated with the placement of infants on their stomachs (prone sleep position) for sleep. The "Back to Sleep" (now "Safe to Sleep") campaign was launched in the United States in 1994 and embodies a public health effort encouraging families to place infants on their backs (supine sleep position) to sleep. Since the start of this campaign, SIDS rates have dropped 50% in the United States. Medical professionals have observed similar drops worldwide, highlighting the importance of the supine sleep position for infants.

Other factors increasing the risk for SIDS include exposure to cigarette smoke, bed-sharing or co-sleeping, over-bundling or the covering of the infant's head by bed covers, loose bedding, or blankets. Recent research studies suggest that breastfeeding, pacifier use, and room-sharing but not bed-sharing for the first year of life may reduce the risk of SIDS. Additional information regarding infant care practices and SIDS risk is available at

How do medical professionals diagnose SIDS?

Sudden infant death remains an unpredictable, unpreventable, and largely inexplicable tragedy. The baby is seemingly healthy without any sign of distress or significant illness prior to the incident.

  • Death occurs rapidly while the infant is sleeping.
  • Typically, it is a silent event. The baby does not cry.
  • The infant usually appears to be well developed, well nourished, and is generally felt to be in good health prior to death. Minor upper respiratory or gastrointestinal symptoms due to viruses like respiratory syncytial virus (RSV) are not uncommon in the last two weeks preceding SIDS.

Sudden, unexpected infant death (SUID) is a general term used for the circumstance of an infant death that occurs suddenly and in an unexpected manner. SIDS is a diagnosis of exclusion, meaning that medical professionals must rule out other causes of death, including sleep environment factors. The cause of an infant's death can be determined only through a process of collecting information and conducting, at times, complex forensic tests and procedures. All other recognizable causes of death are investigated prior to making the diagnosis of SIDS.

Four major avenues of investigation aid in the determination of a SIDS death: postmortem lab tests, autopsy, death-scene investigation, and the review of victim and family case history.

  • Postmortem laboratory tests are done to rule out other causes of death (for example, electrolytes are checked to rule out dehydration and electrolyte imbalance; bacterial and viral cultures are obtained to evaluate whether an infection was present). In SIDS, these laboratory tests are generally not revealing.
  • An autopsy provides clues as to the cause of death. In 15% of sudden, unexpected infant deaths specific abnormalities of the brain or central nervous system, the heart or lungs, or infection may be identified as the cause of death. The autopsy findings in SIDS victims are typically subtle and yield only supportive, rather than conclusive, findings to explain SIDS.
  • A thorough investigation of the death scene consists of interviewing the parents, other caregivers, and family members, collecting items from the death scene, and evaluating that information. A detailed scene investigation may reveal a recognizable and possibly preventable cause of death. Death scene investigations have helped to identify factors in the infant sleep environment that are potentially unsafe. These include soft, padded, or plushy objects that may obstruct an infant's airway, posing a suffocation hazard.
    • A parent or caregiver may be asked these questions:
      • Where did you discover the baby?
      • What position was the baby in?
      • Were there any objects within the sleep location that could have interfered with normal infant breathing?
      • When did you last check the baby? Last fed?
      • How was the baby sleeping?
      • Where there any recent signs of illness?
      • Was the infant taking any medication, either prescription or over the counter?
  • You should let your doctor know about any family or infant medical history. Family history to note would include any previous history of unexplained infant death, sudden cardiac death, and metabolic or genetic disorders, for example.

Latest Healthy Kids News

Trending on MedicineNet

Is it possible to prevent SIDS?

There is currently no way to predict which infants are at risk for SIDS. SIDS has links to certain infant-specific and sleep-environment factors. Therefore, observing the following precautions has reduced the risk of SIDS for many infants.

  • Sleep position and the local sleep environment: Educate babysitters, day care providers, grandparents, and everyone who cares for your baby about SIDS risk and the importance of observing the latest advice related to safe infant sleep offered in the original "Back to Sleep" campaign and updated in the recent "Safe to Sleep" initiative. Safe to Sleep ( messages highlight the importance of the back sleep position with emphasis on safety surrounding the infant sleep environment and safe sleep conditions:
    • Back to sleep: You should place your baby on his or her back to sleep at night and nap time.
      • You should avoid fluffy, loose bedding in your baby's sleep area.
      • Keep your baby's face clear of coverings.
      • Be careful not to overheat your baby by overdressing or adding unnecessary covers.
      • Don't allow anyone to smoke around your baby.
      • Use a firm mattress in a safety-approved crib with a tight fitting sheet. Avoid the use of infant positioning devices.
      • Have your baby sleep in your room (room-share) for the first six to 12 months of life.
      • Do not allow your baby to sleep alongside (bed-share with) another person. The risk of unintentional smothering is too great.
      • Keep all "well-child" appointments, including immunizations.
  • Home monitoring: Medical professionals do not recommend the use of home cardiorespiratory monitors for infants perceived to be at risk of SIDS. Doctor-prescribed monitors are available that sound an alarm if the baby's breathing or heartbeat stops.
    • Current studies still echo the National Institutes of Health (NIH) Consensus Report on SIDS. To date, no reports scientifically demonstrate the effectiveness of home monitoring for siblings of SIDS victims (babies born after a family has had a child die of SIDS).
    • Currently, certain guidelines exist for use of home cardiorespiratory monitoring:
      • Infants with one or more life-threatening episodes in which the baby turned blue or became limp requiring mouth-to-mouth resuscitation or vigorous stimulation and during hospitalization are identified as having abnormal control of heart or lung function.
      • Symptomatic preterm infants with apnea of prematurity and other complications related to premature birth.
      • Infants with certain diseases or conditions that include central (brain related) breathing irregularities
      • If families have questions related to the use of home monitors, they should seek assistance from their child's primary medical care provider.

Does the supine (back) sleep position cause any problems for infants?

Recent studies have evaluated the effect of back sleeping on an infant's motor development. Babies younger than 1 year of age who slept on their backs showed slightly decreased upper trunk strength as reflected in mild delays in their ability to crawl, sit upright unassisted, or pull to stand.

  • However, it is important to emphasize that face-up sleepers still attained these milestones within the accepted time range for normal development. No significant difference in gross motor development was seen by the time either infant group started to walk.
  • Parents should incorporate a certain amount of tummy time while the infant is awake and observed. This type of play while baby is on his or her tummy is recommended for developmental reasons and may also help to prevent flattening of parts of the skull, called plagiocephaly, from developing or persisting on the back of the head.

What support is available to parents who are coping with an infant loss due to SIDS?

Most areas within the United States have access to support services for families following a SIDS death. Each family's grief is unique. However, many families that have experienced SIDS have found it helpful to use the counseling resources that may be provided through public health nursing agencies, local coroner, or medical examiner offices, or information and bereavement programs based at many children's hospitals across the country.

Losing a child is a unique crisis for any family, especially when the child has died suddenly, unexpectedly, and for no apparent reason.

  • Do not blame yourselves! Losing a child to SIDS is not your fault.
  • There are typically no warning signs or symptoms that you could have recognized or prevented.

Grieving is a normal process when dealing with the loss of a loved one. Family, friends, neighbors, workplace, or faith communities may all serve as sources of support. It is important to remember that you are not alone. There are formal support groups and counseling programs available to help you cope with your loss. For further information, you may contact these groups:

First Candle (SIDS Alliance)
49 Locust Avenue, Suite 104
New Canaan, CT 06840

National Institute of Child Health & Human Development
NICHD Information Resource Center
1-800-505-CRIB (2742)
TTY: 1-888-320-6942
Fax: 1-866-760-5947
Mail: PO Box 3006, Rockville, MD 20847
[email protected]

Subscribe to MedicineNet’s Pregnancy & Newborns Newsletter

By clicking “Submit,” I agree to the MedicineNet Terms and Conditions and Privacy Policy. I also agree to receive emails from MedicineNet and I understand that I may opt out of MedicineNet subscriptions at any time.

Where can people get more information about sudden infant death syndrome (SIDS)?

The National Institute of Child Health & Human Development about SIDS and Safe Infant Sleep

U.S. Department of Health and Human Services, Centers for Disease Control and Prevention (CDC) site on SIDS

American Academy of Pediatrics


Most Popular