This has recently become really big. You have a party to reveal the sex of the baby to everyone at once. It can be a small get together or all out party... People can guess what they think the baby is... wear the color they think the baby is... there are lots of different ways people have the party. The one I went to was all out, you wore a ribbon with a pink or blue ribbon (which reflected your guess). They had a board where people guessed what the baby was and people on the winning side got a small prize... all the food was pink and blue. I had a really fun time. Just another way to celebrate the new baby basically.