Description

• The sudden death of an infant <1 year of age that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history
• Sudden infant death syndrome (SIDS) was first formally defined in 1969. The definition was revised in 1989.
• System(s) affected: Cardiovascular; Endocrine/Metabolic; Nervous; Pulmonary
• Synonym(s): Crib death; Cot death

Epidemiology

• SIDS can affect any infant, but some infants are at higher risk than others, including African Americans and American Indians/Native Americans, males, infants whose mothers smoked/used illegal drugs during pregnancy, and several others described below.
• There is a characteristic age pattern, with deaths peaking at 2–4 months, and more deaths occurring during the colder seasons.

• For 2008: All races: 0.55/1,000 live births (2,350 cases/yr):
  • White non-Hispanic: 0.55/1,000 live births (1,238 cases/yr)
  • African American non-Hispanic: 1.07/1,000 live births (665 cases/yr)
  • Hispanic: 0.32/1,000 live births (328 cases/yr)
  • Native American: 0.91/1,000 live births (45 cases/yr)
  • Asian/Pacific Islander: 0.23/1,000 live births (59 cases/yr)
• Predominant age: Uncommon in 1st month of life; peak occurs between 2 and 4 months of age; 90% of deaths occur by 6 months of age.
• Predominant sex: Male > Female (52–60% male)

Pediatric Considerations
Occurs only in infants

Risk Factors

• Although some infants may die from SIDS who have no apparent risk factors, most have ≥1 of the following risk factors associated with SIDS:
  • Race: African Americans and Native Americans have highest incidence.
  • Season: Late fall and winter months
  • Time of day: Between midnight and 6 A.M.
  • Activity: During sleep
  • Low birth weight; intrauterine growth retardation (IUGR)
  • Poverty
• Maternal factors:
  • Younger age
  • Decreased education
  • Maternal use of cigarettes/drugs (e.g., cocaine, opiates) during pregnancy
  • Higher parity
  • Inadequate prenatal care
• Respiratory/GI infection in recent past
• Sleep practices:
  • Prone and side sleep positions
  • Overheating from heavy clothing and bedding and/or elevated room temperature
  • Soft bedding
  • Bed sharing
  • No room sharing
• Passive cigarette smoke exposure after birth
• No pacifier use
• No breastfeeding

Genetics
Emerging evidence for genetic risk factors, especially related to impaired brain-stem regulation of breathing or other autonomic control, impaired immune responses, and cardiac ion channelopathies associated with long QT syndrome and fatal arrhythmia

General Prevention

Because a SIDS death is sudden and the cause is unknown, SIDS cannot be “treated.” However, some measures may be effective in reducing the risk of SIDS (2)[B]:

• Maternal avoidance of cigarette smoking and illicit drug use during pregnancy
• Avoidance of passive cigarette smoke exposure
• Avoidance of the prone (face-down) and side sleep positions, excessive bed clothing, and soft bedding such as pillows, comforters, and bumper pads or a soft mattress
• Avoidance of overheating
• A crib, bassinet, or cradle conforming to federal safety standards is the recommended sleeping location.
• Avoidance of bed sharing with the infant, particularly by adults other than the parent(s) or by other children. Bed sharing should be avoided if the mother/father has used cigarettes, drugs, or alcohol. Bed sharing on couches is very dangerous and should never be done.
• Infants who sleep in the same room as their parents (without bed sharing) have a lower risk of SIDS. It is recommended that infants sleep in a crib/bassinet in their parents' bedroom, which when placed close to their bed will allow for more convenient breastfeeding and contact.
• Breastfeeding is associated with a decreased risk of SIDS and is recommended for all infants (3)[B].
• Pacifier use is associated with a reduced risk of SIDS:
  • Consider offering a pacifier at bedtime and nap time.
  • Delay the introduction of the pacifier among breast-fed infants until 1 month of age (4)[B].
  • Pacifier use has not been found to be detrimental to breastfeeding if it is introduced after the baby is 1 month of age, when breastfeeding is well established (5)[A].
• Avoidance of commercial devices marketed to reduce the risk of SIDS
• It is critical that all people caring for infants, including daycare providers, be instructed in these risk-reduction measures.
• Newborn nurseries should implement these recommendations well before discharge so parents see appropriate practices modeled.

Pathophysiology

Strong evidence for a respiratory pathway that includes the following stages:

• A life-threatening event causes severe asphyxia and/or brain hypoperfusion. This can include rebreathing exhaled carbon dioxide in a face-down position.
• The vulnerable infant does not wake up or turn his/her head in response to asphyxia, resulting in further rebreathing and inability to recover from apnea.
• Progressive apnea leads to hypoxic coma.
• Bradycardia and hypoxic apnea occur.
• Autoresuscitation fails, resulting in prolonged apnea and death (6).

Etiology

• There are many theories. There may be subtle developmental abnormalities resulting from pre- and/or perinatal brain injury, which make the infant vulnerable to SIDS.
• Possible causes:
  • Abnormalities in respiratory control and arousal responsiveness
  • Central and peripheral nervous system abnormalities
  • Cardiac arrhythmias
  • Rebreathing in face-down position on soft surface, leading to hypoxia and hypercarbia
  • SIDS may occur when ≥1 environmental risk factors interact with ≥1 genetic risk factors.

Commonly Associated Conditions

Infants are generally well, or may have had a mild febrile illness (i.e., gastroenteritis or an upper respiratory infection) prior to death.