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Sudden infant death syndrome

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Sudden infant death syndrome is the commonest cause of death in the first year of life, causing one to two deaths per thousand livebirths.

By definition, sudden infant death syndrome (SIDS) does not have a cause (1,2):

  • sudden death of an infant under one year of age which remains unexplained after a thorough case investigation, including the performance of a complete autopsy, examination of the death scene, and review of the clinical history (3)

The incidence of sudden infant death has fallen in the past decade

  • were 247 unexplained deaths of children under 2 years of age in 2014; of these, 230 were unexplained infant deaths, giving a rate of 0.30 deaths per 1,000 live births (3)

  • commonest at 3 months
    • is uncommon until 2 to 4 months when it is the highest, following which it declines (2)
    • around 90% of deaths happen within six months of age (2)
    • at a 60:40 ratio, males are more inclined to die than females (2)

  • more common in Winter and cities

  • Sweden has a 1/4 the rate of the UK

General improvement in population health has resulted in a lower incidence of SIDS, and risks can be significantly reduced by (1,2,3,4):

  • baby sleeping in the same room as parents
    • safest place for an infant to sleep is on a separate surface designed for infants close to their parent's bed (2)
    • sleeping in the parent's room on a separate surface can reduce the risk of SIDS by 50% (2)

  • baby sleeping on a separate surface to parents

  • placing babies on their backs to sleep
    • in several Western regions, it is recommended to lie down supine and in a bed other than put nearer to adults to avoid Sudden Infant Death Syndrome (SIDS) (2)
    • an infant placed in the prone position while sleeping has been shown to increase the risk of SIDS by 14-fold and causes additional stress on the cardiovascular and respiratory systems (2)
    • once babies are strong enough to roll over and back, parents do not need to repeatedly roll them back as the ability to roll over is protective (1)

  • avoiding overheating, including:
    • following the "feet to the foot" advice: a baby is placed at the foot of the cot with the blanket tucked in on three sides to reduce the risk of covering the head
    • removing cushions and soft toys from the cot to reduce the risk of smothering
    • keeping the baby's room relatively cool, at about 18 degrees C

  • avoiding cigarette smoke

  • breastfeeding, either exclusively or partially

  • using a pacifier or dummy (without attachments)
    • risk of SIDS had reduced with the usage of pacifiers (2)
    • use of pacifiers in infants older than one month is currently advised by numerous researchers to prevent sudden infant death syndrome (2)
    • due to the risk of strangulation, pacifiers shouldn't be placed around infants' necks (2)
      • pacifiers attached to toys or other items may lead to suffocation/choking

  • many parents sleep with the baby in their bed when the baby won't settle. Discuss with them the association between SIDS and co-sleeping, and that the risk to the infant is greater when sleeping on a sofa or chair
    • NICE state:
      • with respect to bed sharing
        • discuss with parents safer practices for bed sharing, including
          • making sure the baby sleeps on a firm, flat mattress, lying face up (rather than face down or on their side)
          • not sleeping on a sofa or chair with the baby
          • not having pillows or duvets near the baby
          • not having other children or pets in the bed when sharing a bed with a baby.
        • strongly advise parents not to share a bed with their baby if their baby was low birth weight or if either parent:
          • has had 2 or more units of alcohol
          • smokes
            • children born to mothers who both drank and smoked have a 12-fold increased risk for SIDS (2)
          • has taken medicine that causes drowsiness
          • has used recreational drugs

Recently much focus has been placed on the unknown subset of infants perishing from what has been described as sudden infant death syndrome, but who have in fact been the victims of more definable illnesses, including inborn errors of metabolism and abuse ( identification of metabolic syndromes has led to better understanding, management, and avoidance of some of these deaths, for example medium chain acyl CoA dehydrogenase deficiency). It is for these potentially preventable reasons that sudden infant death syndrome should be regarded as a diagnosis of exclusion, and careful examination and investigation be carried out in each and every case. This is never more true than when more than one child in a family has died.


  • Wacogne I, Drinnan K. Ask the expert: common problems in new babies in primary care BMJ 2023; 382 :p1489 doi:10.1136/bmj.p1489
  • Vincent A, Chu NT, Shah A, Avanthika C, Jhaveri S, Singh K, Limaye OM, Boddu H. Sudden Infant Death Syndrome: Risk Factors and Newer Risk Reduction Strategies. Cureus. 2023 Jun 17;15(6):e40572. doi: 10.7759/cureus.40572. PMID: 37465778; PMCID: PMC10351748.
  • Garstang J, Pease AS. A United Kingdom Perspective. In: Duncan JR, Byard RW, editors. SIDS Sudden Infant and Early Childhood Death: The Past, the Present and the Future. Adelaide (AU): University of Adelaide Press; 2018 May. Chapter 18. Available from:
  • National Institute for Health and Care Excellence (NICE). Postnatal care. NICE guideline NG194. 2021

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