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Sudden infant death syndrome 

Sudden infant death syndrome
Sudden infant death syndrome

Jeremy Hull

, Julian Forton

, and Anne Thomson

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Subscriber: null; date: 23 October 2019



The sudden death of an infant that is unexpected on the basis of the history and unexplained by a thorough post-mortem examination and by examination of the scene of death.


The incidence is 0.5 per 1000 live births. It is the commonest cause of death in infants between 1 month and 1 year of age; 90% occur in the first 6 months of life. It is commoner in boys.

Risk factors

  • Sibling with sudden infant death syndrome (SIDS).

  • Maternal smoking.

  • Maternal drug abuse.

  • Maternal age <20 years (2.6-fold increased risk).

  • Prematurity.

  • Low birthweight (<2500 g; 3-fold increased risk).

  • Late or no prenatal care.

  • Sleeping prone (6-fold increased risk) or on side.

Theories of causation

  • Immature respiratory control fails to compensate for imposed physiological stresses.

  • There may also be abnormal or immature control of temperature, chemoreceptor sensitivity, and heart rate responses.

  • A deficit in sleep arousal in response to cardiorespiratory disturbance appears to be necessary for SIDS to occur.

  • The imposed stresses may include URTI, overheating, and partial airways obstruction (by secretions or external material such as the infant’s bedding).


  • Supine sleeping posture.

  • Avoid maternal smoking pre- and post-natally.

  • Avoid overheating during sleep. Use sheets and thin blankets, not duvets. Avoid pillows.

  • Avoid the head becoming covered during sleep—arms outside sheets, feet at the bottom of the cot.

  • Use a firm mattress, and do not place soft toys in the cot.

  • Avoid parental sleeping on the chair or sofa with the infant.

  • Avoid sleeping in the same bed as the parent.

  • The safest environment for sleep seems to be in a cot in the parents’ room.

  • Encourage breastfeeding

  • The use of pacifier (dummy) is associated with decreased incidence

Immediate management of sudden infant death syndrome

Most hospitals will have a written policy for the management of SIDS.


  • The vast majority of SIDS victims will be brought to hospital by ambulance.

  • The paramedic crews will have started resuscitation.

  • How long resuscitation is continued is a matter of judgement. On some occasions, it will be obvious that this infant has been dead for some hours. In other cases, it will be appropriate to continue for the standard 30 min, after which, if there have been no signs of cardiac or respiratory activity, care should be withdrawn.

  • It can be important for the parents to be present during resuscitation attempts, so that they can see that everything that could be done was done. If parents are present, they need to have a member of staff with them at all times to explain what is happening.


In addition to the standard history, additional information is needed. This will usually require a separate meeting with the parents, often the following day. If possible, this meeting should be carried out in the parents’ home.

  • Any previous medical problems?

  • Any recent change in health?

  • When was the baby last seen alive? (Where and by whom?)

  • Exactly how was he/she found (position, covers, clothing, room temperature)?

  • Details of resuscitation carried out at home.

  • Family structure.

  • Family history of SIDS.

  • Consanguineous parents?

  • Description of usual sleeping arrangements.

  • Bed sharing when found (with whom?).

  • Smoking in pregnancy.

  • Parental smokers (one or both).

  • Parental alcohol (in last 24 h). Who? How much?

  • Parental drug use (in last 24 h). Who? What?


Consent from the parents is required for the collection of samples. After death, the body comes under the jurisdiction of the coroner, who has control over any subsequent measures that affect it. Advance agreement in principle with the local coroner for sample collection should be in place. It may be necessary to carry out a cardiac puncture to obtain sufficient blood.

  • FBC.

  • Sodium (Na), potassium (K), calcium (Ca), magnesium (Mg).

  • Urea and creatinine.

  • Glucose.

  • Albumin.

  • Alanine aminotransferase (ALT).

  • Aspartate aminotransferase (AST).

  • Alkaline phosphatase.

  • Plasma amino acids.

  • Acyl carnitine (collect a blood spot on a Guthrie card).

  • Blood culture.

  • Urine (suprapubic aspiration, SPA) for culture, amino and organic acids, and toxicology.

  • Throat swab.

  • Rectal swab.

  • Nasal swab.

  • Lumbar puncture.

Skin biopsy may be necessary but can nearly always wait, until the autopsy is performed.

Informing other parties

The following individuals will need to be informed.

  • The coroner has a duty to investigate all sudden and unexpected deaths and must be informed. An autopsy will need to be performed. The responsible paediatrician will need to provide the coroner with a report, based on their interview with the parents and any other relevant material (including information from the GP).

  • The police will have to talk to the parents, and the parents may have to identify the baby in their presence.

  • The responsible consultant paediatrician.

  • The GP.

  • The health visitor (the infant will need to be removed from the immunization register).

  • The Child Death Review organizer (statutory process to ‘conduct a comprehensive, multidisciplinary review of child deaths, to better understand how and why children die, and use the findings to take action that can prevent other deaths and improve the health and safety of children’).


A multidisciplinary meeting, involving the pathologist, the paediatrician, and the primary health care team, should be convened when the data from the autopsy are available. The purpose of the meeting will be to establish the likely cause of death and to identify any precipitating factors. The results of the meeting should be conveyed in a written report to the parents.

Further information

The Lullaby Trust. Available at: <>.

The Royal College of Pathologists and The Royal College of Paediatrics and Child Health (2004). Sudden unexpected death in infancy. The report of a working group convened by The Royal College of Pathologists and the Royal College of Paediatrics and Child Health. Available at: <>.