It's a smaller party than a shower for a mother-to-be who is NOT having a first baby. You are supposed to bring "smaller" gifts than for a shower (whatever that means).
Keep in mind , we had a full blown shower for this guest of honor when she had her first baby a few years ago. I purchased a lovely gift for her then.
Here's the deal -- I think the more appropriate thing is for people to send the new baby a gift after he/she has been born, if they feel like it.
IMO "Sprinkle" is just a code word for "2nd shower", which is just not cool.