Its a lovely idea - they actually suggest people do this with cloth nappies for the bitty babies in NICU and SCN, they suggest mum wears a cloth nappy under her shirt for a day or so then to pop it in with bub for comfort.

Its a great way for bub to feel some sort of security when it is alone

On the flip side - I read somewhere for parents to do this with a shirt or blankey and get babies smell along with the parents smell for pet dogs and cats so they get an association with this new little bundle before it comes home