The talk-show host hadn't publicly discussed the impending new addition to his family and her birth came as a shock to many. In a recent interview with the "Today" show's Savannah Guthrie, he revealed that they used a surrogate. She showed a sneak peek of the full interview that will air next week.
"It wasn't really a secret," he said about the pregnancy, "but my wife and I have been trying for a while to have a baby. And so we've tried a bunch of things. And so we had a surrogate."
He said that this time they decided not to tell anybody about the pregnancy. "It'd just be more fun if it was just private between me and my wife, and we get to introduce her to everybody. When it happened, we were shocked!"
In the clip above, Guthrie comments on how Fallon is "filled with joy" over his first child. There's no doubt that he'll kill it at this whole dad thing.