Don't say BABY!
When each guest arrives give them a nappy pin or a tiny baby figurine. Once all guests have arrived tell them they aren't allowed to say the word baby for the duration of the party. If anyone hears someone else say baby he or she can steal this pin or baby. The person with the most amount of pins at the end of the party is the winner.
Name the baby
Have a sheet of paper with A-Z on it and people have to fill out a name for each letter in the gender that you are expecting. The person with the most names wins.
How Big is My Belly? Pass a ball of wool around and people have to cut lengths of the size they think your belly is. The person with the closest length of string wins.
Melt down chocolate and candy inside diapers and have your guests guess what is in each diaper. Person with the most correct guesses wins.
My Waters Have Broke
Freeze tiny baby figurines in a block of ice. Each person is given 1 block of ice and has to suck on it until it melts. No biting. First person to successfully melt their ice block yells my water broke and wins the game.
Paint the Onesies
Buy a plain white onesie for each guest and get them to use baby safe paint to paint it. Now you have a whole hand painted wardrobe for your baby.
Give a single nappy to each guest and have them write a short note on them for you. Now each nappy time you will have something that will make you smile or laugh.
Play Dough Babies
Give each person 3 small balls of play dough in different colours and ask them to make babies depicting the gender you are expecting. The best made baby wins.
Porn or Labour
Print out a serious of facial expressions from both porn and labour images and have your guests guess which category each image falls into. Person with the most correct guesses wins.