M.R.
We had a "sprinkle" for a friend's third baby. It was a small celebration, and the organizing friend specified that it would be "dutch." Invitees can choose to go or not to go. Nothing wrong with celebrating a new baby! Even a fun group lunch can be special for a pregnant mom, gifts or not. Go for it! :)
p.s., yes I'd go, and yes I'd assume I'd pay my own way.