Mark Zuckerberg and his wife Priscilla Chan are expecting a baby girl, the Facebook CEO announced on his page. He also revealed that the pair had been through three miscarriages over the past few years. "You feel so hopeful when you learn you're going to have a child," Zuckerberg wrote. "You start imagining who they'll become and dreaming of hopes for their future. You start making plans, and then they're gone. It's a lonely experience."