SAN FRANCISCO » Talk about birth announcements: Facebook CEO Mark Zuckerberg and his wife said they’ll devote nearly all their wealth — roughly $45 billion — to good works in celebration of their new baby daughter, Max.

Zuckerberg’s wife, Priscilla Chan, gave birth to a 7-pound, 8-ounce daughter last week. But the couple didn’t put out the news until today, when Zuckerberg posted it on — of course — Facebook.

In the same post, Zuckerberg said he and Chan will commit 99 percent of their Facebook stock to such causes as fighting disease, improving education and “building strong communities.” They are forming a new organization, called the Chan Zuckerberg Initiative, that will pursue those goals through a combination of charitable donations, private investment and promotion of government-policy reform.

“Like all parents, we want you to grow up in a world better than ours today,” the social media mogul and his wife wrote in a letter to their daughter, which they also posted on Facebook.

In the letter, they described their goals as “advancing human potential and promoting equality” and added: “We must make long term investments over 25, 50 or even 100 years. The greatest challenges require very long time horizons and cannot be solved by short term thinking.”

Zuckerberg promised to release more details in the future. But he said the couple will transfer most of their wealth to the initiative “during our lives.” In a statement, Facebook described the initiative as not a foundation but “a limited liability company controlled by Mark and Priscilla.”

The Facebook co-founder and chief executive is one of the world’s wealthiest men. He and Chan, a pediatrician, have previously donated large sums to public schools in Newark, New Jersey and the San Francisco Bay Area, along with the Zuckerberg San Francisco General Hospital, where Chan did her medical training.

But Zuckerberg told the Associated Press in an interview last month that he has no plans to step down as CEO of Facebook. In a statement, the company also said the couple’s plan to transfer their shares over time won’t affect his status as controlling shareholder of the company.

In addition, Zuckerberg has committed to dispose of no more than $1 billion of Facebook stock every year for the next three years, the company said.