How do most people celebrate the birth of their first child? Maybe they commemorate the arrival of a little bundle of joy by sending out cute notices in the mail, taking myriad baby photos, or even passing out the traditional cigars at work. But when Mark Zuckerberg, founder and CEO of Facebook, and his wife, Priscilla Chan, gave birth to a baby girl, Max Zuckerberg, he celebrated the occasion with what is possibly the most generous and selfless act in modern history: he gave away his fortune.

Well, it wasn’t his entire fortune, but Zuckerberg announced that he’ll be giving away 99% of his own personal shares in Facebook to charity. How much is that auspicious gift worth? According to various analysts, that could add up to around $45 billion dollars (yes, that’s billion with a B) just from Facebook shares.

When Max came into this world on an undisclosed day last week, weighing 7 lbs. 8 ounces, her parents penned a letter titled ‘A Letter to our Daughter’ and posted it publically online, along with their first family photo. The 2,200-word letter outlines their plans to donate 99% of his Facebook shares over the course of his lifetime to the newly formed Zuckerberg Chan Initiative. In the letter, they talk about the universal issues of health, education, community building, Internet access and learning, and pledge to “advance human potential and promote equality” through their Initiative – and with their donation.

While that may ring the bell as the biggest charitable donation ever, it’s certainly not out of character for Zuckerberg, who has already committed about $1.6 billion to charitable causes this year. But believe it or not, there is a bigger picture to this already jaw-dropping philanthropic gesture.

Zuckerberg’s gift on behalf of baby Max was the start of his commitment to the Giving Pledge. Started by investment mogul and billionaire Warrant Buffet five years ago, The Giving Pledge. Buffet started The Pledge along with fellow multi-billionaires Bill and Melinda Gates, of Microsoft fame and themselves huge philanthropists, as part of a movement designed to urge billionaires to give away the majority of their wealth to charity.

The Giving Pledge was formally introduced in 2010 and efforts to persuade America’s wealthiest individuals to commit to donating at least half of their fortune to charity and good causes over the course of their lifetime, or in their will. The pledge is not a contract or legally binding, but a moral commitment.

To date, more than 130 ultra-wealthy individuals or couples from 14 countries have volunteered for The Giving Pledge. Notable “pledgers” include Oracle (ORCL, Tech30) CEO Larry Ellison (estimated net worth: $54.3 billion), Michael Bloomberg ($35.5 billion), famed investor Carl Icahn ($22.2 billion), Microsoft (MSFT, Tech30) co-founder Paul Allen ($17.5 billion), Telsa (TSLA) founder Elon Musk ($13.3 billion), as well as Sara Blakely, inventor of Spandex, George B. Kaiser, oil and banking tycoon, Russia’s richest man, Vladimir Potanin, Harold Hamm and Sue Ann Arnall, whose children convinced them to sign The Pledge, and Manoj Bhargava, inventor of Five Hour Energy drinks.

Now, we can add Mark Zuckerberg and Priscilla Chan to that list, a gracious and heart-warming gift to welcome their baby daughter, Max, into this world.

But it’s not just about the dollars given away, as the website states that The Pledge’s mission is also to “inspire conversations, discussions, and action, not just about how much [to give] but also for what purposes and to what end.”