When do you size up diapers ?


My girl is 6 weeks and still wearing newborn clothes (starting to wear some 0-3) and newborn diapers. She is getting too long for the newborn diapers but the size 1s are so saggy on her butt and seem to big. She eats a TON for a 6 weeker but still feels so little, she’s much smaller than all the other babies in her daycare class.