Understanding SIDS

What is SIDS?

Sudden infant death syndrome (SIDS) is the sudden, unexplained death of an infant, usually between the ages of one and six months. SIDS is also called "crib death". 

What causes SIDS?

Nobody yet knows what actually causes SIDS.  Many healthcare providers and researchers now believe that SIDS is not a single condition that is always caused by the same medical problems. Rather, SIDS may be caused by several different factors.

  • Some experts believe that SIDS babies are born with differences in their brains that make them unable to wake up from sleep when they are breathing high carbon dioxide or low oxygen levels; this leads to abnormal breathing or heart function.
  • Researchers have found that infants who eventually died from SIDS tend to have more trouble waking up during the night than other infants. Infants who die from SIDS also tend to wake up partially more frequently and for a longer period of time in the first part of the night and completely wake fewer times during the latter part of the night.
  • Scientists are beginning to find differences in genes and DNA that may make infants more vulnerable to SIDS.
  • SIDS may be a result of incorrect brain signals due to irregular brain chemistry.
  • Specific risk factors for SIDS have been identified. The most important are:
  • A mother's smoking during pregnancy
  • Placing the infant on its tummy to sleep, which can cause the baby to breathe in too much carbon dioxide and not enough oxygen
  • Secondhand smoke in the home

Other risk factors include:

  • Bed sharing with parents or others
  • Soft bedding in the crib
  • Multiple birth babies
  • Male babies
  • African-American babies
  • American Indian/Alaska Native babies
  • Premature babies
  • Babies with a sibling who died of SIDS
  • Mothers who smoke or use illegal drugs
  • Teen mothers
  • Short time between pregnancies
  • Late or no prenatal care
  • Poverty

Whom does SIDS affect?

Some babies are more likely to die of SIDS than others:

  • Male babies more than female babies
  • Premature and low birth weight babies more than full-term babies and those of normal birth weight
  • African American and American Indian/Alaska Native babies more than babies of other races or ethnic groups
  • Infants who share a bed with parents or others more than babies who sleep alone
  • SIDS is most likely to occur in babies between two and four months old, and 90 percent occur by six months of age. SIDS occurs more often in winter months, with the peak in January.

How common is SIDS?

  • SIDS is the third-ranking cause of death for infants under one year of age.
  • The overall SIDS rate has dropped throughout the United States, but there are differences among racial and ethnic groups.
  • African American and American Indian infants are 2.1 and 1.9 times more likely, respectively, to die from SIDS than White infants.