Multiple sources tell Usmagazine.com the supermodel, 28, and her husband, Tom Brady, 31, are expecting their first child together.
On Wednesday, Bundchen hit the catwalk in a bump-hiding mini dress for Sao Paulo Fashion Week Spring-Summer 2010 in her native Brazil.
Bundchen wed Brady in Santa Monica, Calif. last February, as first reported by Us. They tied the knot again in Costa Rica in April.
Brady is dad to John Edward Thomas Moynahan, born in 2007, with ex Bridget Moynahan.
In an interview with Vanity Fair, Bundchen said she felt the kid was "100 percent" hers
"I want him to have a great relationship with his mom, because that's important, but I love him the same way as if he were mine," she said.
"I feel grateful because I have a lot of love in my life. I found the person I'm sharing my life with. I have a good man," she continued.