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Learn About Sudden Infant Death Syndrome (SIDS)

Sudden Infant Death Syndrome (SIDS) is the sudden and unexpected death of an infant less than 1 year of age from an unknown cause. SIDS is unpredictable and affects seemingly healthy babies.

Key Facts:

  • SIDS is the leading cause of death between 1 month and 1 year of age.
  • SIDS remains unpredictable with an unknown cause despite years of research.
  • The risk of SIDS can be greatly reduced by avoiding key associated factors, such as placing infants on their stomachs or sides for sleep and smoking by the mother.

How Common Is SIDS?

SIDS is the leading cause of unexpected deaths in infants in developed countries. In 2013, between 1,500 and 2,000 infants in the United States died of SIDS. SIDS is more common in boys than girls. African-American and Native American infants are about three times more likely to die from SIDS than Caucasian infants. SIDS is also more common in premature infants.

When Does It Happen?

SIDS usually occurs during sleep and is thus often referred to as "crib death." Although SIDS may occur at any time during the first year of life, these events happen most often between 2 and 4 months of age when the infant's sleep patterns are still developing. SIDS is also more common during the cold weather months. Ninety percent of these deaths occur in infants up to 6 months old.

Why Does SIDS Happen?

Although risk factors have been identified, the precise cause of SIDS is unknown. The risk is greatest when the following three factors are present:

  1. A vulnerable infant (i.e., born prematurely or exposed to maternal smoking while in the womb)
  2. During a time of developmental instability such as when sleep patterns are maturing
  3. Being placed on the stomach to go to sleep. These infants are thought to have immature breathing reflexes resulting in a failure to awaken from sleep resulting in death.

Usually, more than one of these factors contributes to SIDS.

    This content was developed in partnership with the CHEST Foundation, the philanthropic arm of the American College of Chest Physicians.

    Page Last Updated: July 30, 2019

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