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Sudden Infant Death Syndrome (SIDS)

  • Definition

    Article updated and reviewed by Daniel A. Rauch, MD, FAAP, Associate Professor of Clinical Pediatrics, Associate Residency Program Director and Director of Pediatric Hospitalist Service, New York University. Editorial review provided by VeriMed Healthcare Network on May 2, 2005.

    One of the most devastating tragedies that can befall young parents is the sudden death of their infant. When the death is unexplained by history or a thorough examination, including an autopsy, it is defined as sudden infant death syndrome (SIDS). SIDS is the leading cause of death in infants between the ages of one month and 12 months in the U.S. and has an incidence of 1-2/1000 live births or 5,000 to 6,000 deaths per year. This translates into one third to one half of all deaths in the one month to one year age group.


    The peak age for SIDS is two to four months, and it most often occurs during sleep. More cases happen during winter months, but SIDS can occur any time of year. Certain groups of infants are at a somewhat higher risk, including premature infants, boys, and infants born to substance-abusing mothers. Other risk factors are tobacco smoke exposure and prone sleeping position (face down). In the United States there is a higher rate among African-Americans. There are currently no diagnostic tests to identify individual infants at risk.

    There is often little or no warning for the shocked parents, with less than 10 percent of SIDS victims having had a history of apparent life threatening events (ALTEs). ALTEs are characterized by some combination of apnea (cessation of breathing), color change (usually pale or blue/gray), and choking or gagging, and are understandably frightening to the observer, who may fear that the infant has died. Previous terms to describe these incidents as "aborted crib death" or "near death" wrongly imply a close association between ALTEs and SIDS. In fact, most infants with an ALTE do not subsequently have SIDS.


    How great is the risk of SIDS in subsequent births?

    What can be done next time to prevent it?

    Are there any signs or symptoms we should have been aware of?

    Would the use of a home monitor diminish the risk?

    By definition, the cause of SIDS is unknown. In fact, it is likely that SIDS is the end result of many different processes. That makes prevention of all SIDS a difficult task.

    New evidence suggests that a subtle form of suffocation may be the true culprit in one-quarter to one-half of all suspected SIDS cases. There is strong evidence that the prone position in which babies sleep (face down) is associated with SIDS. Several studies, particularly those from Australia and New Zealand, have linked the prone position to elevated SIDS risk. Based on the careful evaluation of numerous studies, health officials now want to change the way American babies sleep in the hope of preventing SIDS. The campaign to educate parents about the importance of sleep position for babies is called "Back to Sleep" and is supported and endorsed by the Surgeon General's Office, the U.S. Consumer Product safety Commission and the American Academy of Pediatrics.

    The specific advice is to let the baby fuss on his or her back (for no more than a few minutes) during the first few months of life before calming him down and trying again. If you try for 20 to 30 minutes three nights in a row and the baby still will not go to sleep on his back, let him fall asleep on the stomach and then turn him onto his back or wait a few days and try positioning him again. Parents can buy special wedges that help maintain the baby’s position on the back or side. Furthermore, babies should not be placed asleep on any blankets or with any pillows or stuffed animals. The goal is to not have any objects that can block the baby’s face and hinder breathing.

    The underlying mechanism for these cases of SIDS appears to be an abnormal response to stressors such as changes in blood levels of oxygen or carbon dioxide. This may explain the high frequency in the first half year of life that subsequently declines with increasing developmental maturity.

    Another cause that has been postulated is a specific heart dysrhythmia called prolonged QT syndrome. Although this can be screened for, it is unclear what the exact risk is and if treatment would be successful. Still another cause is metabolic defects.

    Unfortunately, some cases of SIDS are due to infanticide. This possibility makes a thorough examination of each case all the more important.

    Home monitoring has long been utilized as preventative measure in higher risk children and those who have already experienced an ALTE. However, there is almost no evidence to suggest that home monitoring is effective for this purpose.

    Precautions to reduce the chance of SIDS

    • Have good medical care and adequate nutrition during pregnancy.
    • Keep baby in smoke-free surroundings (smoking by either parent as well as secondhand smoke are clearly linked with SIDS).
    • Put baby to sleep on a firm mattress.
    • Breastfeed, if possible.
    • If "blue spells" are noticed in the infant, get prompt medical advice.
    • Try not to let the baby get too hot (don't over-swaddle).
    • Never have the infant's face covered by bedclothes.
    • Avoid thick blankets, pillows or bumpers in the crib.
    • Try not to let the infant sleep on his/her stomach.
    • Put the baby to sleep on his/her side or back. (A rolled-up towel along his/her back will help to keep the baby on his/her side.)

    Babies seem to be at above-SIDS risk where the following conditions are present:

    • in winter time
    • if their mothers smoke cigarettes during and/or after pregnancy
    • if their mothers are drug addicts
    • if their mothers received insufficient health care while pregnant (poor uterine environment)
    • if parts of the baby's brain that regulate breathing remain immature (delayed development) - perhaps due to short bouts of oxygen shortage
    • if infants are overheated (faulty body temperature control) - Over-swaddling or heavy bedding may make the body work too hard to keep down body temperature.
    • if babies are overweight at birth, slow to gain weight or premature - especially with lung disorders
    • if they have had serious apnea (temporary breathing stoppage). Several "blue spells" may signal a flaw in breathing control.
    • if bottle-fed rather than breastfed.