The usual medical term is ‘Sudden Unexpected Death in Infancy’ (SUDI) or Sudden Unexpected Death in Childhood (SUDC), if the baby was over 12 months old.

Some sudden and unexpected deaths can be explained by the post-mortem examination revealing, for example, an unforeseen infection or metabolic disorder. Deaths that remain unexplained after the post mortem are usually registered as ‘Sudden Infant Death Syndrome’ (SIDS) or SUDC in a child over 12 months. Sometimes other terms such as SUDI or ‘unascertained’ may be used.

‘Cot death’ was a term commonly used in the past to describe the sudden and unexpected death of an infant. It has largely been abandoned, due to its misleading suggestions that sudden infant death can only occur when a baby is asleep in their own cot, which we know to be untrue.

What causes SIDS?

A thorough post-mortem examination will reveal a specific cause of death in less than half of all sudden infant deaths. Causes may include accidents, infection, congenital abnormality or metabolic disorder. For the deaths that remain unexplained (SIDS), researchers think there are likely to be undiscovered causes. For many it is likely that a combination of factors affect a baby at a vulnerable stage of development.