Facebook CEO Mark Zuckerberg declared that he and his wife Priscilla Chan will donate 99 percent of their Facebook shares to charity over the course of their lives.

The announcement was made via Facebook on Dec. 1. The couple also celebrated the birth of their new baby girl, Max Chan Zuckerberg.

In the lengthy open letter, addressed to his infant daughter, Zuckerberg said he wanted to make sure Max grew up in a world better than today.

"While headlines often focus on what's wrong, in many ways the world is getting better. Health is improving. Poverty is shrinking. Knowledge is growing. People are connecting. Technological progress in every field means your life should be dramatically better than ours today," Zuckerberg wrote. "We will do our part to make this happen, not only because we love you, but also because we have a moral responsibility to all children in the next generation."

According to Forbes' Real Time Billionaires ranking, Zuckerberg is the 7th richest person in the world, with an estimated net worth of $46.8 billion. If he and his wife fulfill their promise, $45 billion of that will be donated to charity.

In the letter, Zuckerberg also called attention to the Chan Zuckerberg Initiative, which he says will help advance their missions of curing disease, building communities and bringing personalized education to children around the world.

It is uncertain how exactly the couple's Initiative will tie in to the donations, though Zuckerberg said they will share more details in the coming months. Zuckerberg joined the Giving Pledge in 2010, promising to eventually give away at least half of his net worth. It's clear the billionaire intends to go above and beyond his initial commitment.

According to Forbes, Zuckerberg's pledge was made official through a filing with the Securities and Exchange Commission, which states: "On December 1, 2015, our Founder, Chairman and CEO, Mark Zuckerberg, announced that, during his lifetime, he will gift or otherwise direct substantially all of his shares of Facebook stock, or the net after-tax proceeds from sales of such shares, to further the mission of advancing human potential and promoting equality by means of philanthropic, public advocacy, and other activities for the public good. For this purpose, Mr. Zuckerberg has established a new entity, the Chan Zuckerberg Initiative, LLC, and he will control the voting and disposition of any shares held by such entity."