Naturally, of course, people should RSVP and let you know if they’re going to attend. It’s the polite thing to do, without question. But polite is one of those eye of the beholder terms; and people who haven’t invested several days of their life to putting a memorable baby shower together may not realize how impolite they're being by just showing up, unannounced.

So how do you solve this problem? Well, like all good solutions: you head it off before it becomes a problem! While you want to have all of your invitees RSVP, you should make it utterly clear that you’d like a response regardless of whether they'll attend. To that end, depending on the size of your baby shower guest list, you should include a self-addressed stamped envelope and a self-typed note with each invitation that says something like this:

You can create any variation of this as you want. This is just a simple little sample that highlights the things that you should ask: whether a guest is attending, or not. In other words, you don’t want any grey area here; you don’t want a default that says: I didn’t reply, so I’m not coming. Politely and tastefully, a little note like the one above obliges your invitee to actively let you know whether they’ll show up or not.

Now, if your baby shower guest list is smaller and it’s feasible to do so, you may want to skip the mailing campaign and just phone people up instead. If you have the time and the ability to do so (that is, the guest list is small enough for you to manage), this is actually preferred. It gives your invitees the opportunity to ask questions, such as where mom-to-be is registered or whether she has any special gift requests (as when Grandma has already purchased 57 outfits in newborn size, but diapers are still sorely needed).