system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Sudden Infant Death Syndrome (SIDS).
gpt
SIDS is the sudden, unexpected death of an infant who is less than 1 year old when there is no other identifiable cause.

We don't know what causes it because it's a catch-all label.  It's kind of like checking "other" on a multiple choice question.  If the baby was healthy and there's nothing else obviously wrong we call it SIDS.

That said, it typically happens 1) to infants between 2-4 months 2) while they are sleeping and 3) the "Back to Sleep" campaign has made death from SIDS somewhat rarer.

The "Back to Sleep" campaign is a public health awareness campaign telling parents to put their kids to sleep on their backs instead of their stomachs and away from any big puffy blankets.  (There are other things that have been related to SIDS, though, like genetics or parents who smoke.)

So: many SIDS deaths are probably caused by some sort of suffocation or something similar.  But not all of them!