My understanding is that SIDS prevention is basically different ways to stop babies getting into a super super deep sleep that they don't wake up from for whatever (unknown) reason, or ways to stop them getting smothered.
Of all the things that increase the likelihood of super deep deep sleep (laying on belly or curled up, no pacifier, warmer temperature, sleeping on parent, swaddling etc), what increases deep sleep the least ie. Which rule break increases the risk of SIDS the least?
Sometimes baby just will not sleep in their safe space, so if co sleeping in the bed isn't an option with an exhausted parent, why is the sofa so bad?
If the parent is sat holding the baby with their arms propped up on cushions either side in a way that neither the baby (laying on their back) or the parents arms can't move when the parent is asleep/fully relaxed, what's the problem? No chance of baby getting wedged in pillows or being dropped on floor.
Note: I'm not including things that increase suffocation risk like heavy blankets, arms under blankets, smoking, bed sharing with pets/drunk parents, cot bumpers, teddies in crib etc
Edit: can to can't, typo