I would ask them why they want the scan. Is it just to see how big bub is? Or are there other medical situations that measuring ahead could indicate? If it's to check that there's not something wrong then they could just check that and not measure size! If it's just so they can tell you how big bub is and try to induce you I definitely wouldn't be getting the scan.

Big What a PITA! You are making the perfect sized bub for you.