"I slept like a baby". How many times have you used that or heard someone else make that claim? A statement that implies a deep, still sleep. Has anyone making this claim actually slept with a baby?
Still they are not. The little blighters wriggle and move and kick and punch and slap and scratch. Quiet they are not. Grunting, snorting or making some loud exclamations at whim. Babies sleeping do not imply a restful night for me. Not any more.
You would think that a balled fist the size of a cherry tomato could not do any harm to a full grown and resilient adult. You would think that a weeny foot half the size of a cell phone could not cause an "oof" or some other type of grunt to escape from the same full grown adult. You'd be wrong.
Sleeping beside the offspring (in as deep a sleep as is possible for a new parent) thinking that junior is in fact sleeping deeply and immobile, one is suddenly woken by a kick in the solar plexus, a punch in the face, a kick in the boob, a scratch on the cheek or some other form of physical-ness that indicates the youngster has gotten a fright or that you really need to be awake now to attend to their needs.
Of course there is the odd occasion when the little 'un will wake quietly and allow you a few minutes grace. There has been more than one instance when the Big Maori has woken face to face with the Little Maori. Opening my eyes to find a smaller yet very open and wide gaze staring intently at the bigger version, or big ugly nose to small cute button one, tip to tip.
So the cute factor will always apply with the term "sleeping like a baby", but for me now, if I want to imply I slept soundly without actually saying that, I'd be more inclined to use "I slept like a log" or "I slept like the dead". These two things really don't move.