Sudden Infant Death Syndrome (SIDS) is the phenomenon of infants dying suddenly and unexpectedly with no apparent cause, often called cot death or crib death. This occurs throughout the world, although the total number of children who die from this is hard to determine. Particularly in third world countries, there may be a huge range of reasons why infants might die, and picking out the sudden unexplained ones may be difficult.

In non-third-world countries, SIDS is the most common cause of death in the post-perinatal period. Most deaths occur between 1 and 7 months, although the accepted age range for SIDS is between 2 weeks and 2 years old.

Males are statistically slightly more likely to suffer from it; however, this is true of many kinds of death and isn't due to any of the features of SIDS specifically. Twins are also slightly more likely to suffer from it; partially this is because twins are more likely to be born prematurely.

It is also more common in winter, and in poorer families.

Nobody knows what causes SIDS. However, the rate has been reduced in recent years by a campaign informing parents to do the following:

  • sleep the baby on its back
  • do not smoke during pregnancy or around the child
  • do not overheat the baby by wrapping it too tightly
Countries where this advice hasn't been given out haven't had a reduced rate of infant mortality.