Brady confirmed in a television interview scheduled to air Sunday that Bundchen is pregnant. Brady also has a child with ex-girlfriend Bridget Moynahan.
Brady told ESPN: "It couldn't be harder than this training camp, so I'll be prepared."
Bundchen did a photo shoot for London Fog recently, and a company spokesman said this summer that the pictures were airbrushed to remove her baby bump.
Brady had previously denied reports that Bundchen was pregnant.