100% cotton onesies from petit bateau (my Costco had them) are NOT pre-shrunk.
the 12mo onesies I bought look like they're 0-3m. Apparently you're never supposed to put them in the dryer from what I can tell by the tag, which is kinda ridiculous for baby clothes IMO.
I'll be returning them to Costco if possible. I don't think buying a larger size would help, as I know I will forget to dig through wet laundry to find them.
Re: baby clothes PSA : petit bateau = fail