Diaper sizes for baby

So I’m having my second child in a few months. My first baby was almost 9 pounds so I’m assuming this one will be the same. I know newborn size goes to 9 pounds, and size 1 is 8 - 14 pounds. If she’s born already 9 do I even buy newborn sizes or should I just buy size 1? I know I should remember but I don’t lol