Facebook founder and CEO Mark Zuckerberg shared a major status update Thursday: He announced on his Facebook and Instagram pages that he and wife Priscilla Chan are expecting their second child.

"Priscilla and I are happy to share we're expecting another baby girl!" Zuckerberg, 32, wrote in a post that included photos of the couple when they were children.

They are already parents to their 15-month-old daughter Maxima, whom they call Max.

Zuckerberg also wrote about the difficulties that Chan, a pediatrician, had getting pregnant.

"After our difficult experience having Max, we weren't sure what to expect or whether we'd be able to have another child," he wrote. "When Priscilla and I first found out she was pregnant again, our first hope was that the child would be healthy. My next hope was that it would be a girl. I cannot think of a greater gift than having a sister and I'm so happy Max and our new child will have each other."