I feel a bit mean excluding mum from what would no doubt be a huge experience for her. However, I also want to keep the scan as a special "just DH and me" moment (and bubs of course!). Also, heaven forbid, if a problem was revealed at the scan, I'd prefer time for DH and I to get our heads around it before having my entire family know (which they would if Mum were there).

I just know I'm also going to have a similar problem at the birth. I'll definitely want it to be just DH and I, but Mum and Dad are planning to arrive in town a couple weeks before my due date so that they'll be here, and I know that she'll be hoping for an invite!
Sweetie, you feel mean because your mother wants to muscle in on something that is YOUR special moment? Just tell her it's you and DH only, same as for the birth. I really don't understand where these mothers get off in guilting us into spoiling our most precious times because of their selfishness.