When do you know its time to upgrade diaper size? My MIL keeps saying its almost time to go up a size...her way of saying they are already too small. But they seem to fit fine...the yellow tape still almost touches each other. The diaper doesn't leak. Hes in newborns last weight check he was at 9.7 and I know weight wise i believe for the next size its 10. But even at his weight he is still a small baby.