"Actress Christina Applegate and fiancé, musician Martyn LeNoble, welcomed daughter Sadie Grace LeNoble on Thursday, Jan. 27, 2011 in Los Angeles," the spokesperson said in a statement. "Mother and daughter are doing great."
Adds someone close to the proud parents: "She's a beautiful little girl, and they are so happy and in love with her."
Applegate, 39, and LeNoble, 41, have been dating for nearly three years and became engaged last Valentine's Day. The pregnancy was announced in July.
In August, Applegate told PEOPLE: "I'll probably be a little bit hippie and a little bit Type A. I'll take from what my mother did, which was way hippie and like, 'Do what you wanna do,' and bring some things that I know from watching my friends raise their kids. An amalgamation of sorts."