Size 1 or 2!

My daughter is 4 months old and is wearing size 1 still. She does have a tiny waist and never leaks out of them even overnight. She has a dr appointment tomorrow so I’m going to check her weight but I weighed her at home and she is 13lb and I know diapers go by weight. Does size 2 look to big? Should I still keep her in 1’s?