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Sudden Unexpected Death in Infancy (SUDI)

What is SUDI?

The sudden and unexpected death of a baby is usually referred to by professionals as ‘sudden unexpected death in infancy’ (SUDI). The death of a baby which is unexpected is also sometimes referred to as ‘sudden infant death’.

Some sudden and unexpected deaths can be explained by a post-mortem examination, however deaths that remain unexplained are usually registered as ‘sudden infant death syndrome’ (SIDS). Sometimes the term ‘unascertained’ may be used.


SUDI Risk Factors

  • A baby sleeping in an unsafe position (prone or side)
  • A baby sleeping in an unsafe environment (co-sleeping, overwrapping, soft sleeping surfaces etc.)
  • Tobacco (during pregnancy and environmental exposure)
  • Alcohol and drugs (during pregnancy and when co-sleeping)
  • Poor post-natal care (late booking and poor antenatal attendance)
  • Low birth weight (under 2,500g) and pre-term birth (less than 37 weeks’ gestation)


Supporting Parents with Safer Sleep

A key role for professionals is to support parents to apply safer sleeping practice for their babies particularly where situational risk or ‘out of routine sleeping’ may be a factor. Key examples are:

  • Temporary housing
  • Altered sleeping arrangements (holidays, family occasions, staying with relatives, illness, fleeing domestic abuse)
  • Planned use of alcohol and prompting arrangements to maintain safer sleep practices
  • Deprivation and poverty indicators, overcrowding
  • Adverse childhood experiences / impact on key messages being understood
  • Late booking and poor antenatal/postnatal engagement
  • Evidence of neglect, domestic abuse and parental criminality


The National Picture

Over 300 babies and young children still die every year from SUDI in the United Kingdom. National research coordinated by the Lullaby Trust has established some key modifiable factors associated with an increased risk of SUDI.

In July 2020 the National Child Safeguarding Practice Review Panel published a thematic report on SUDI which described the findings from a review into SUDIs in families with known vulnerabilities.


SAFER is a sleep advice mnemonic for professionals to use when visiting and observing infants in the home environment:


In November 2021, the Merton Safeguarding Children Partnership (MSCP) received a recommendation from a Joint Agency Response (JAR) Meeting to undertake a Partnership Review on two cases of Sudden Unexpected Death in Infancy (SUDI). Although the Local Authority concluded that neither of the SUDI cases met the criteria for a Serious Incident Notification, the JAR identified that there could be learning for multi-agency partners from both cases. The review sought to identify any relevant learning for the MSCP and recommendations for improved practice. You can read more about this learning by reading the final report.


The Lullaby Trust raises awareness of sudden unexpected death in infancy, provides expert advice on safer sleep for babies and offers emotional support for bereaved families


Babies Cry, You Can Cope (ICON) programme supports parents and carers to manage normal infant crying and to prevent abusive head trauma injuries to babies caused by shaking, also referred to as ‘shaken baby syndrome’ ICON Infant Crying and how to Cope. You can also view the MSCP’s dedicated ICON and Abusive Head Trauma page.


The MSCP Pre-birth Guidance provides a framework for multi-agency working so that there is a clear system is in place to respond to concerns for the welfare of an unborn child and/or where there may be concerns following their birth