Sudden infant death syndrome is the leading cause of infant death beyond the neonatal period.
Incidence roughly 1 in 2000 infants.
Peak incidence between 1 and 3 months of age, although events may occur up to 12 months of age.
Risk factors include exposure to tobacco smoke (antenatally and postnatally); prone and side sleeping; bed-sharing during sleep; a sleep environment that includes soft mattress and/or sleeping surface (including sofa or armchair), and placement of soft sleep bedding; over-bundling/over-heating; prematurity; exposure to alcohol, cannabis, opiates, and illicit drugs (antenatally and postnatally); and viral infection. Several risk factors may co-exist in any given patient.
Protective factors include use of a dummy during sleep, immunisation, and breastfeeding.
Careful evaluation of death by trained forensics teams is necessary to rule out other causes of death, including suffocation, asphyxia, entrapment, infection, ingestions, metabolic diseases, arrhythmia-associated cardiac channelopathies, and trauma (accidental or non-accidental).
The term 'sudden infant death syndrome' (SIDS) was first used, and an early definition described, at the 2nd International Conference on the Causes of Sudden Death in Infants in 1969. In 1991, an expert panel convened by the National Institute of Child Health and Human Development defined SIDS as the sudden death of an infant under 1 year of age with the cause of death unclear after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and a review of the clinical history. The American Academy of Pediatrics use the following definition for unexplained sudden death in infancy or SIDS: ‘The sudden unexpected death of an apparently healthy infant aged <1 year, in which investigation, autopsy, medical history review, and appropriate laboratory testing fail to identify a specific cause, including cases that meet the definition of SIDS’. Some have advocated the addition of the criterion that onset of the fatal event seems to be associated with sleep.
History and exam
Key diagnostic factors
- presence of risk factors
Other diagnostic factors
- absence of metabolic disease
- absence of irritability, lethargy
- absence of fever, cough, or nasal congestion
- absence of trauma
- side, prone, or inclined position at last sleep
- soft sleeping surface/environment
- maternal cigarette smoking
- increasing number of smokers in house
- smoking in same room as child
- formula feeding
- non-use of a dummy
- premature birth
- maternal substance use/abuse
- single parent
- lower maternal age
- low level of antenatal care
- low level of maternal education
- low socio-economic status
- lack of immunisation
Investigations to consider
- blood culture
- cerebrospinal fluid culture
- urine culture
- serum chemistry
- urine chemistry
- photographic record
- skeletal survey
- anatomical pathology
- vitreous chemistry
- muscle biopsy
carers and family
Rachel Y. Moon, MD, FAAP
Professor of Pediatrics
University of Virginia School of Medicine
RYM is an unpaid board member of the International Society for the Prevention of Infant Death. She is chair (unpaid) of the American Academy of Pediatrics Task Force on sudden infant death syndrome. She is principal investigator or co-investigator on several NIH grants. She also receives a small amount of royalties (~USD100/year) for authoring several books.
Dr Rachel Y. Moon would like to gratefully acknowledge Dr John W. Berkenbosch, a previous contributor to this topic.
JWB declares that he has no competing interests.
Peter Fleming, MB ChB, PhD
Professor of Infant Health & Developmental Physiology
FSID Research Unit
Institute of Child Life and Health
St Michaels Hospital
PF is an author of a number of references cited in this topic.
Thomas Hegyi, MD
Professor and Vice-Chair
Department of Pediatrics
UMDNJ-Robert Wood Johnson Medical School
TH declares that he has no competing interests.
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