This game requires a number of baby bottles equal to the number of guests at the party.
Each person is given a bottle filled with juice, water, milk or some other (hopefully tasty) liquid. Everyone must drink from the bottle until their bottle is empty. The person who finishes their bottle first is the winner.
At the end of the party, the mom-to-be gets to take home all of the bottles (be sure to sanitize these for her first!) The winner of the game should receive a prize, perhaps a bottle of wine.