It's not just baby clothes it's all clothes which is why buying clothes online is a right pain in the system XD I remember someone (can't remember who now) who was complaining about a similar thing but with shirts they'd bought for themselves, they bought a bunch of shirts that were the same size on the label and laid them out in a row and the size difference was hilarious. Apparently a couple were all right, but one was a very snug fit (as in I don't think they were comfortable wearing it) and the another they were swimming in.

We lucked out in the baby clothes department, inherited pretty much an entire wardrobe and also had relatives desperate to buy baby clothes so I think we only ended up buying a couple of pieces in our prepatory we have no idea what we're doing but we apparently need some of this stuff phase with the first child XD Inheriting all the clothes was great though as we were then able to use most of the money we didn't spend on baby clothes on a big stash of cloth nappies.