"We're so excited and [I'm] nervous as a first time mom, but it's something I always wanted," she told co-anchors Matt Lauer and Savannah Guthrie. "We've been able to keep it a secret ... longer than most."
Bush Hager, a correspondent for the morning program, was also joined on the couch by husband, Henry. "We have so much to look forward to," he said.
So what does the former president want his future grandchild to call him? "Sir!" he joked.
Bush Hager, who married Henry in 2008, is due in the spring.
Watch her announcement: