Reese Witherspoon - Michael Buble Trusted Reese Witherspoon With Baby Secret

Actress Reese Witherspoon was one of the first people to know that Michael Buble was set to become a father - because the Canadian crooner spilled the baby secret to her during a phone call to discuss a potential duet.

The Home hitmaker learned his model wife Luisana Lopilato was pregnant last autumn (12) and the baby surprise gave him the confidence boost he needed to pick up the phone and call Witherspoon to propose the idea of recording a track together.

And the singer had been so excited about the prospect of parenthood, he entrusted the movie beauty and new mum with the gossip months before announcing the news to fans in January (13).

He tells U.S. radio host Ryan Seacrest, "We loved (her Johnny Cash biopic) Walk the Line and her voice was so smooth and wonderful. So my manager said, 'Call her.' And I said, 'I don't want to put her in that position.' Then my wife came home and told me, 'Mike, we're pregnant.' And I was so happy I was like, 'Today's the day, I'm going to call her'...

"It felt so good to get it (baby news) off my chest, and she was so cute and excited (for us)."

The unlikely collaborators hit the studio late last year (12) and Buble was blown away by Witherspoon's vocal talents: "She was so prepared. In one take, she nailed it."

Witherspoon gave birth to her third child, baby Tennessee, in September (12).