To an extent, yes. Begonias want to be cozy in their pots and will thrive if they are able to fill them out before you move them. Of course, you do not want them to get overly root bound. When it is time to relocate your begonia to a larger container, just choose one size bigger. If you try and increase the pot size too much at once, you might promote root rot. The American Begonia Society provides detailed instructions on potting and repotting begonias.