Several factors have been identified that increase an infant’s risk for SIDS.

Risk Factors for SIDS

1. Tummy (prone) or side sleeping
   Infants who are put to sleep on their tummy or side are more likely to die from SIDS than infants who sleep on their backs.
2. Soft sleep surfaces
   Sleeping on a waterbed, couch, sofa, or pillows, or sleeping with stuffed toys has been associated with an increased risk for SIDS.
3. Loose bedding
   Sleeping with pillows or loose bedding such as comforters, quilts, and blankets increases an infants risk for SIDS.
4. Overheating
   Infants who overheat because they are overdressed, have too many blankets on, or are in a room that is too hot are at a higher risk of SIDS.
5. Smoking
   Infants born to mothers who smoke during pregnancy are at increased risk of SIDS. Also, infants exposed to smoke at home or at daycare are more likely to die from SIDS.
6. Bed sharing
   The safest place for an infant to sleep is in their own crib or other separate safe sleep surface next to the parent or caregiver’s bed.
7. Preterm and low birth weight infants
   Infants born premature or low birth weight are more likely to die from SIDS.

Sudden Unexplained Infant Death (SUID)

Sudden, unexplained infant deaths are defined as deaths for which the cause of death is unknown. These deaths may be still under (or needing further) investigation or they may have completed a thorough investigation and determined the death to be SIDS. When first discovered, many infant deaths do not have an obvious cause. These sudden, unexplained (unexpected) infant deaths, which include suffocation, poisoning, falls, SIDS, and others (see list below), may not be easily distinguishable from one another. None is due to a chronic disease or illness and none is explainable without a more careful examination.

For a medical examiner or coroner to determine the cause of the death, an investigator(s) needs to conduct a thorough investigation including examination of the death scene and a review of the infant’s clinical history. A complete autopsy needs to be performed ideally using information the investigator has gathered. Even when a thorough investigation is conducted, it may be difficult to separate SIDS from other types of sudden, unexplained infant deaths. After the cause of death has been determined, infant deaths that were initially classified as sudden, unexplained infant death can be referred to as sudden, unexpected infant deaths since they are no longer unexplained deaths.

What are causes of Sudden Unexplained Infant Death (SUID)?

• Accidental suffocation or strangulation in bed
  (e.g., the infant suffocates while trapped between an adult bed frame and the wall)
• Other accidental suffocation or strangulation
  (e.g., the infant suffocates by a plastic bag)
• Accidental poisoning
  (e.g., the infant eats some adult aspirin that were left on a coffee table)
• Obstruction of respiratory tract
  (e.g., the infant chokes on a coin, food, or other object)
• Accidental falls
  (e.g., the infant falls down the stairs)
• Neglect, abandonment and other maltreatment syndromes
  (e.g., the infant dies after being left alone for a period of time)
• Assault and homicide
  (e.g., the infant dies after someone harms them on purpose)
• Other symptoms, signs and abnormal clinical and laboratory findings not elsewhere classified
  (e.g., the infant dies of unknown cause, or unexplained heart or breathing failure)

SUIDI Reporting Form
The SUIDI reporting form is a guide for novice and veteran investigators of infant deaths. The form is designed to ensure that all information is collected in a consistent, sensitive manner. The form is designed as a questionnaire ...more

SIDS Support and Bereavement*

SIDS and Vaccination

Search PubMed for articles on SIDS
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Page last reviewed: 3/15/08
Page last modified: 3/15/08
Content source: Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion