Dubbed "opera's coolest soprano", the Australian singer told the magazine that she was in San Francisco when she discovered the news.
Danielle De Niese and Gus Christie outside their home
"I was in the middle of rehearsals, and I went and got a couple of pregnancy tests then immediately called Gus", she said, before adding: "I told him the good news on Facetime - well, when you travel..."
Gus is the chairman of the annual Glyndebourne festival, where Danielle first came to fame following her performance as Cleopatra in Giulio Cesare at the 2005 festival. The pair now live at Glyndebourne, the country estate which houses the famous opera house.
Danielle De Niese in 2014
Their new addition is due in May and will also grow up at Glyndebourne, with Danielle admitting: "My husband was born in the house. He was warm memories of the influx of characters here and sitting in the orchestra pit with his brother."
Danielle has no plans to step back from performing though, and confirmed that she will be starring in a double bill of Ravel at the festival in July.
See the full exclusive story in HELLO! Magazine, out now.