Growth scan at third trimester

Hi mummies, i read up about growth scan usually to be done in third trimester, I’m at week 27 and mentioned about this scan during my routine check up yesterday, but my gynae said don’t need to do it since he don’t see any problem with my baby. Is this the usual practice? Anyone didn’t do the growth scan also? Can i go do this scan myself without gynae’s referral? Thank you. #1stimemom #advicepls