My son was born at 8lbs 15oz and wore nb for about 2 weeks. i knew it was time to go up to 1 because he was leaking constantly, he has a smaller waist and the 1 seems slightly big but ever since i switched he stopped leaking he weighs 9lbs 7oz or more now.

if the size ones r to big and the nb r getting tight u can always fold over the top then put the straps on! my son is 8 months old and in size 4 diapers and their a little big so thats wat i do

All I know is size 1s are cheaper! Lol. I switched but my babies little legs are skinny and she always leaks out of the size 1

NB goes up to 8lbs. it doesn't make sense to try and force her into something that doesn't fit cause then you end up with a mess. If you as her mom see there's no issue then don't switch until you feel she has grown out of it

They go by weight, but if they fit and aren't leaking I would keep her in them a little longer, I'm having to do that with my daughter she would be over the weight but since she has a smaller waist i keep her in the smaller ones if she isn't leaking

Once it's getting tight around her legs u need to move up. My son is 5 months and in 1s. He wore preemies for 5 weeks then wore newborns till he was almost 4 months old. He was 5 weeks early