Mark Zuckerberg (R), founder and CEO of Facebook, and wife Priscilla Chan arrive on the red carpet during the 2nd annual Breakthrough Prize Award in Mountain View, California November 9, 2014.[Photo/Agencies]

About $350 billion is given away each year in the United States by charities, said Stacy Palmer, editor of the Chronicle of Philanthropy. She said Zuckerberg and his wife Priscilla Chan's announcement was remarkable not just because of the size of the donation, but because of their ages.

"Our lists of the top donors are usually dominated by people in their 70s or 80s," she said. "This is a message to other young people who are deciding what to do with their great wealth."

In welcoming the birth of his first child on his Facebook page, Zuckerberg posted a photo of himself, his wife and their new daughter, Maxima, nicknamed Max, along with a post entitled "A letter to our daughter."

In the 2,220-word letter, Zuckerberg and Chan touched on issues including health, education, Internet access and learning before announcing the Chan Zuckerberg Initiative, which aims to "advance human potential and promote equality." They plan to give away 99 percent of their Facebook shares over their lifetimes to advance the initiative, which was formed as a limited liability company controlled by the two. It will begin by focusing on curing disease, Internet connectivity, community building and personalized learning - or the idea that technology can help students learn at different paces.

Maxima Chan Zuckerberg was born early last week — though Facebook did not specify her birth date — and weighed 7 lbs 8 ounces (3.4 kg) at birth. Last month, Zuckerberg announced he would take two months of paternity leave after the birth. Chan and Zuckerberg have so far committed $1.6 billion to their philanthropy. They have given several donations this year, including to public schools, initiatives to bring better wireless Internet access and to San Francisco General Hospital, where Chan works as a pediatrician. Zuckerberg and Chan said they will share more details when they return from their maternity and paternity leaves.

Zuckerberg has started his leave, a company representative said, and will be available if "absolutely needed." Sheryl Sandberg, chief operating officer, and Mike Schroepfer, chief technology officer, will run the company in Zuckerberg's absence.