Mark Zuckerberg and his wife, Priscilla Chan

Facebook Inc. founder Mark Zuckerberg and his wife, Priscilla Chan, are expecting a second child, a daughter, the billionaire Internet mogul said.

The couple was not sure they would be able to have another child after a difficult pregnancy with their first daughter, born in 2015, Zuckerberg, 32, said in a post on Facebook, the world’s largest social network.

“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,” Zuckerberg, who grew up with three sisters, wrote.

Their first daughter, Max, briefly entered the spotlight last year when Zuckerberg posted a photo of her getting immunization shots and was inundated with Facebook users debating the merits of vaccines.

The announcement came on the same day that Facebook shares hit an all-time of $138.57, riding upbeat expectations for growth as well as recent gains in the broader market.

Zuckerberg has a net worth of $57.8 billion, according to Forbes magazine, although in 2015 he pledged to put 99 percent of his Facebook shares into a new philanthropy project focusing on human potential and equality.

Separately, Harvard announced earlier this week that Zuckerberg, a Harvard dropout, was chosen to address students at a May 25 graduation ceremony on the Cambridge campus.

Harvard President Drew Faust said Zuckerberg “has profoundly altered the nature of social engagement worldwide,” adding that she is glad to welcome him back.

Zuckerberg went to Harvard as an undergraduate in 2002 but left after his sophomore year to pursue his company, which later became Facebook.

He had planned to return to Harvard later but changed his mind after Facebook became a quick success. Director Steven Spielberg gave Harvard’s commencement speech last year.

Related articles across the web

• Harvard dropout Zuckerberg to address grads at alma mater
• The Zuckerberg manifesto: How he plans to debug the world
• Mark Zuckerberg and Priscilla Chan are expecting another baby girl
• Mark Zuckerberg to become father for second time and hopes to raise 'another strong woman'
• Facebook CEO Mark Zuckerberg, Wife Priscilla Chan Welcoming Second Daughter Soon
• 10 things in tech you need to know today (FB, AMZN, SNAP, TWTR, GOOG)
• Zuckerberg envisions Facebook as a 'global community'
• Noted Press Adversary Mark Zuckerberg Shamelessly Panders to Journalists
• Mark Zuckerberg is now paying nearly 50 scientists as part of his plan to cure all diseases (FB)
• Mark Zuckerberg and Priscilla Chan grant first $50 million out of $3 billion to scientists