Kerr's rep confirmed Wednesday in a statement to People that the 34-year-old Australian model is pregnant and "looking forward" to welcoming a baby with Spiegel.
"Miranda, Evan and Flynn are looking forward to welcoming the newest member of their family," the rep said.
The former Victoria's Secret model is already mom to 6-year-old son Flynn, whom she shares with ex-husband Orlando Bloom. She hid any signs of a baby bump Friday in a photo of herself sitting in the grass with her dog.
"Ready for the weekend #marella," the star captioned the picture.
Kerr married Spiegel in Los Angeles in May, and shared photos in July from the "magical" day. She previously told Net-a-Porter she, Spiegel and Bloom maintain a friendly relationship focused on Flynn.
"Our son is our priority, so you have to come from love. You have to be kind," the star said in the magazine's January 2016 issue.
"Orlando thinks [Evan] is great," she shared. "We're just a modern family now!"