Priscilla Chan and Facebook CEO Mark Zuckerberg are new parents.

The couple announced the birth of their first child, a daughter named Max, on Tuesday.

“I am beyond thrilled to introduce you to our Max. Her being fills us with hope and inspires us to join others in creating a better future,” Chan said in a Facebook post.

She then shared a note from Zuckerberg, called “A Letter to Our Daughter”.

In it, Zuckerberg and Chan pledge to give away pretty much their entire Facebook fortune – 99% of their shares. The two will do so under a new charitable mission called the Chan Zuckerberg Initiative.

Zuckerberg and Chan, writing to their new daughter:

As you begin the next generation of the Chan Zuckerberg family, we also begin the Chan Zuckerberg Initiative to join people across the world to advance human potential and promote equality for all children in the next generation. Our initial areas of focus will be personalized learning, curing disease, connecting people and building strong communities.

We will give 99% of our Facebook shares — currently about $45 billion — during our lives to advance this mission. We know this is a small contribution compared to all the resources and talents of those already working on these issues. But we want to do what we can, working alongside many others.

Chan, a medical doctor, married Zuckerberg in 2012 after nearly a decade of dating. She announced her pregnancy in July, and the couple shared their struggles with miscarriages.

“Max, we love you and feel a great responsibility to leave the world a better place for you and all children. We wish you a life filled with the same love, hope and joy you give us. We can’t wait to see what you bring to this world,” said Chan and Zuckerberg in their letter to Max.