My son is 8 days old and weighs 7 lbs 8 ounces. Newborn diapers fit him but he has been peeing through them and soaking his clothes constantly. We started using size 1's and folding the top in and that has helped his leaking. They fit pretty well too.
This. Every time she peed or pooped it would leak all up her back with the n. 1s come higher up her back so by the end of week 1 we had stopped using the n size altogether. Too many blowouts!