Josh Duhamel shares a picture of Fergie's baby bump on Facebook and wishes her a "Happy Mother's-to-be Day." Credit: Courtesy of Josh Duhamel

Expectant father Josh Duhamel gave a special Mother's Day shout-out to his pregnant wife, Fergie, on Sunday, May 12. The 40-year-old actor posted a sweet photo of himself holding her baby bump on Facebook.

"Happy Mother's-to-be day!" he captioned the shot. In the picture, which appears to have been taken at Fergie's sister Dana's Apr. 27 wedding, the couple has big smiles on their faces as they proudly shows off Fergie's growing belly.

Duhamel also tweeted, "Let's remember why we're all here. Tell mom you love her." The Black Eyed Peas songstress, 38, did just that and tweeted, "Happy Mother's Day to my wonderful mommy Terri and all the strong mamas out there." She also added a beautiful old photo of her mom.

Fergie recently told E! News that her husband of four years has been "amazing" throughout her pregnancy. "He so nice and wonderful. He sings and talks to my belly all the time. He's very complimentary," she said. "I'm very lucky that he's really good to me." 

"He's going to be an amazing father," Fergie added. "He's got natural parenting instincts. And he wanted to knock me up on our first date."