We went based on our wedding invite list... BUT word of warning:
My MIL insisted on inviting 25 people that live out of town or out of state. I now feel like that was really gift grabby and I know they probably won't be able to make it but she didn't want anyone to "feel excluded if a local family member brought it up" We pretty muchy sent invites to all the wives from our wedding invitation list (she didn't even know some of their first or last names)!
To top it all off - she is only contributing the cake to the shower cost... I can understand having an indication on the guest list if you were co-hosting but just inviting people "even though they probably won't come" is really annoying...
I wish I would have put my foot down & said no then send a birth announcement to all of these people instead. I'd rather have a smaller shower with people that I actually KNOW there...
Also - DO NOT have your host indicate "Regrets Only" on the invitation - I am really regretting it right now. We have 2 weeks til the shower and only 3 regrets (from over 75 invites) and we know that about 20-25 probably won't come because they live out of town!