Mark Zuckerberg and Priscilla Chan are expecting their first child together

Mark, 31, wrote: "Priscilla and I have some exciting news: we're expecting a baby girl!

"This will be a new chapter in our lives. We've already been so fortunate for the opportunity to touch people's lives around the world

- Cilla as a doctor and educator, and me through this community and philanthropy. Now we'll focus on making the world a better place for our child and the next generation.

"We want to share one experience to start. We've been trying to have a child for a couple of years and have had three miscarriages along the way.

You feel so hopeful when you learn you're going to have a child. You start imagining who they'll become and dreaming of hopes for their future. You start making plans, and then they're gone. It's a lonely experience. Most people don't discuss miscarriages because you worry your problems will distance you or reflect upon you - as if you're defective or did something to cause this. So you struggle on your own."

Mark revealed that they had decided to open up about their previous miscarriages in order to help others.

He wrote: "We hope that sharing our experience will give more people the same hope we felt and will help more people feel comfortable sharing their stories as well."

And Mark said that his 30-year-old wife was far enough in her pregnancy that the risk of something similar happening was low.

He explained: "Our good news is that our pregnancy is now far enough along that the risk of loss is very low and we are very hopeful.

"Cilla and our child are both healthy. We're looking forward to welcoming her into the world and sharing more soon when she's ready to come out and meet everyone!"