Size of baby clothes for newborn?

My baby will be born this Friday (Nov. 27) and I have outfits that are of the 6 month size (Child of mine, by Carters) They are all the fleece, wintery sleepers and I'm worried that she wont be able to fit into them while it's still cold out. Should I return them for the 3 month size? I know I could just wait and see, but I'm anxious and want to do it now. lol