Nobody does not know this rule. They just cannot follow it, and the reason is always the same: your hands are full when you arrive and a nap is on the line. What actually helps is a flat spot you made before you left.
You woke up and the baby is still beside you. What to do in the first thirty seconds, why the couch is a different question, and how to set the bed up before tonight.
Check the chest or the back of the neck, not the hands. The AAP signs of overheating, the NHS room temperature, and the one thing nobody does in the car.
The AAP says stop swaddling at the first sign of trying to roll, which can be as early as 2 months. How tight, arms in or out, and why sleep sacks follow the same rule.
The AAP says babies have no regular sleep cycles until about four months. Why they wake every one to two hours, and what actually makes nights cheaper.