Josh Duhamel, a soon-to-be-father, shared a picture of his pregnant wife on Mother's Day.
Holding her belly, he wrote, "Happy Mother's-to-be day!"
The picture seems to have been taken on Fergie's sister Dana's wedding on April 27.
Duhamel also tweeted, "Let's remember why we're all here. Tell mom you love her."
Fergie followed up with a tweet, "Happy Mother's Day to my wonderful mommy Terri and all the strong mamas out there."
She posted a photo of her mother.
Fergie recently told E! News that Duhamel, her husband of four years, has been amazing while she's been pregnant.
"He's 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. He's got natural parenting instincts. And he wanted to knock me up on our first date."