No, baby beds come in different sizes. However, the standard size of the bed requires to be at least 27 and ¼ inches in length, with a maximum thickness of 6 inches. But remember, that whatever size you choose for the crib, the bed should fit very snug or moderately snug in the crib. As sighted earlier in this article, you should not be able to stick in more than two fingers between the side of the mattress and the crib frame. As you can see, the size of the bed matters a lot, as your child’s safety and comfort lie in it.