My boy is 12 months old but still wearing 9-month outfits from Carter's. This costume fit him nicely with just enough give for crawling around at the playground - and the fabric held up to the rubberized playground service. It was a little tight getting him in and out of the costume, a few more velcro openings really would be needed for a chubbier baby. And changing his diaper would have been really difficult. A handy person could either unstitch the leg openings or the back and add more velcro pieces for getting a slightly bigger baby in and out of the costume. All in all my boy looked totally adorable and won 2nd place in the costume contest.