Sudden infant death syndrome

Last updated: June 29, 2023

Summarytoggle arrow icon

Sudden infant death syndrome (SIDS) is the abrupt and unexplained death of an infant less than 1 year old. Although the etiology of SIDS remains unclear, evidence suggests that it is caused by a combination of environmental triggers and cardiorespiratory impairment, which then leads to prolonged hypoxia. Most cases of SIDS occur in the first 6 months of life. Parents should receive information on how to prevent SIDS during prenatal care and in pediatric check-ups after birth. Recommendations include placing the infant on their back to sleep, ensuring a safe sleep environment (e.g., appropriate sleeping surface and sleepwear, room-sharing with a caretaker, avoiding accessories like pillows and toys) avoiding overheating, and avoiding second-hand smoke. SIDS is a diagnosis of exclusion, and autopsy is required to rule out other causes of death (e.g., congenital cardiac anomalies or battered child syndrome).

Definitiontoggle arrow icon

Sudden infant death syndrome (SIDS) is the abrupt and unexplained death of an infant. [1]

Epidemiologytoggle arrow icon

Epidemiological data refers to the US, unless otherwise specified.

Etiologytoggle arrow icon

The etiology of SIDS remains unclear. Evidence suggests that it is caused by a combination of both extrinsic and intrinsic factors, which ultimately lead to acute or chronic hypoxia. Over 90% of cases of SIDS occur during sleep. [3][4]

Extrinsic factors [4][5]

  • Sleeping in the prone position
  • Exposure to nicotine during pregnancy and after birth (including 2nd-hand smoking)
  • Young maternal age (especially < 20 years)
  • Overheating
  • Unsafe sleeping environment or CO2 rebreathing, e.g., a shared blanket, stuffed animals in the crib, soft bedding

Intrinsic factors [3]

  • Male sex
  • Prematurity
  • Prenatal and/or postnatal exposure to smoking, alcohol, and/or drugs
  • Polymorphisms in the serotoninergic pathway
  • Brainstem abnormality that affects serotoninergic modulation of cardiorespiratory control and impairs protective responses to external stressors

Differential diagnosestoggle arrow icon

SIDS is a diagnosis of exclusion. As with any unexplained infant death, US law requires an autopsy to rule out other causes of death.

The differential diagnoses listed here are not exhaustive.

Brief resolved unexplained event (BRUE; formerly apparent life-threatening event, ALTE)toggle arrow icon

  • Definition: a sudden, brief (< 1 minute), and resolved event without apparent cause occurring in a child < 1 year and involving ≥ 1 of the following:
    • Cyanosis or pallor
    • Absent, decreased, or irregular breathing
    • Change in muscle tone (i.e., hypertonia or hypotonia)
    • Altered level of responsiveness
  • Risk stratification
    • The presence of all the following criteria indicates a low risk of adverse outcomes, recurrence, and serious underlying conditions:
    • Patients who do not meet all of the criteria should be considered at high risk for adverse outcomes, recurrence, and serious underlying conditions.
  • Diagnosis
    • Physical examination and history
    • Diagnosis of exclusion: If a cause for the event can be determined, then it is not BRUE.
  • Management
    • Patients with low-risk BRUE [6]
      • Education for caregivers
      • Recommend CPR training to caregivers
    • Patients with high-risk BRUE [7]
      • Initial evaluation and management
      • Secondary evaluation and management
        • If no cause can be established after primary evaluation, hospital admission for continuous prolonged oximetry, observation, swallow evaluation, and feeding consultation is indicated.
        • Further interventions according to event characteristics

Preventiontoggle arrow icon

Prenatal and well-child care visits should involve education on how to prevent SIDS.

During pregnancy

Protective factors after birth

  • The infant should be placed to sleep in the supine position
  • Safe sleep environment: firm mattress, no pillows, blankets, stuffed animals, or bumper pads in the crib. [9][10]
  • In the first 6 months, co-sleeping in the same room without bed-sharing [11]
  • Smoke-free environment
  • Avoid overheating
  • Use of pacifier during sleep, especially between 1 and 6 months of age [12]
  • Breastfeeding until at least the age of 4 months [13]
  • Placing an infant in a prone position while awake and supervised (tummy time) helps strengthen neck and shoulder muscles.
  • Immunization in line with the official vaccination schedule to prevent infections associated with SIDS

Referencestoggle arrow icon

  1. Kinney HC, Thach BT. The Sudden Infant Death Syndrome. N Engl J Med. 2009; 361 (8): p.795-805.doi: 10.1056/nejmra0803836 . | Open in Read by QxMD
  2. Duncan JR, Byard RW, Duncan JR, Byard RW. Sudden Infant Death Syndrome: An Overview.. University of Adelaide Press ; 2018: p. Chapter 2
  3. Kinney HC, Richerson GB, Dymecki SM, Darnall, Nattie EE. The brainstem and serotonin in the sudden infant death syndrome. Annu Rev Pathol. 2009; 4: p.517-550.doi: 10.1146/annurev.pathol.4.110807.092322 . | Open in Read by QxMD
  4. Jessica Blackburn, Valeria F. Chapur, Julie A. Stephens, Jing Zhao, Anne Shepler, Christopher R. Pierson, José Javier Otero. Revisiting the Neuropathology of Sudden Infant Death Syndrome (SIDS). Frontiers in Neurology. 2020; 11.doi: 10.3389/fneur.2020.594550 . | Open in Read by QxMD
  5. HOFFMAN HJ, DAMUS K, HILLMAN L, KRONGRAD E. Risk Factors for SIDS.. Ann N Y Acad Sci. 1988; 533 (1 The Sudden In): p.13-30.doi: 10.1111/j.1749-6632.1988.tb37230.x . | Open in Read by QxMD
  6. Strandberg-Larsen K, Grønboek M, Andersen AM, Andersen PK, Olsen J. Alcohol drinking pattern during pregnancy and risk of infant mortality. Epidemiology. 2009; 20 (6): p.884-891.doi: 10.1097/EDE.0b013e3181bbd46c . | Open in Read by QxMD
  7. Hauck FR, Herman SM, Donovan M et al.. Sleep environment and the risk of sudden infant death syndrome in an urban population: the Chicago Infant Mortality Study. Pediatrics. 2003; 111 (5.2): p.1207-1214.
  8. Wilson CA, Taylor BJ, Laing RM, Williams SM, Mitchell EA. Clothing and bedding and its relevance to sudden infant death syndrome: further results from the New Zealand Cot Death Study. J Paediatr Child Health. 1994; 30 (6): p.506-512.
  9. Ruys JH, de Jonge GA, Brand R, Engelberts AC, Semmekrot BA. Bed-sharing in the first four months of life: a risk factor for sudden infant death.. Acta Paediatr. 2007; 96 (10): p.1399-1403.doi: 10.1111/j.1651-2227.2007.00413.x . | Open in Read by QxMD
  10. Moon RY, Carlin RF, Hand I, Task Force on Sudden Infant Death Syndrome and the Committee on Fetus and Newborn. Evidence Base for 2022 Updated Recommendations for a Safe Infant Sleeping Environment to Reduce the Risk of Sleep-Related Infant Deaths. Pediatrics. 2022; 150 (1).doi: 10.1542/peds.2022-057991 . | Open in Read by QxMD
  11. Hauck FR, Thompson JM, Tanabe KO, Moon RY, Vennemann MM. Breastfeeding and reduced risk of sudden infant death syndrome: a meta-analysis. Pediatrics. 2011; 128 (1): p.103-110.doi: 10.1542/peds.2010-3000 . | Open in Read by QxMD
  12. Brief Resolved Unexplained Events (Formerly Apparent Life-Threatening Events) and Evaluation of Lower-Risk Infants. Updated: May 1, 2016. Accessed: February 2, 2023.
  13. A Framework for Evaluation of the Higher-Risk Infant After a Brief Resolved Unexplained Event. Updated: August 1, 2019. Accessed: February 2, 2023.

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