Get some ice trays that are designed for larger ice cubes than the regular size. Also buy small plastic babies that would fit inside each ice cube slot, you can usually find these at any party store. Place one plastic baby in each ice cube slot and then fill the tray with water. Make sure you have as many ice cube babies as you have guests and some extras as well. Put the ice trays in the freezer so you will have frozen ice cubed babies.
At the beginning of the shower put one ice cube each in a cup of water and hand one to each guest. As the ice melts the baby will slowly be revealed. When the ice is fully melted and the baby is free floating the player yells “My Water Broke!”
The guest who’s “water breaks” first and the baby is born wins the game! For twins you can use two babies per cube, or two cubes per guest.
This is a game of pure chance so it works really well to break the ice – no pun intended. A perfect door prize game to hand out random prizes, too.