Song written by Pete Townsend. During the musical Tommy, this was the first scene in which Kim actually sang. Before that, during the overture, Kim, playing Mrs. Walker, meets Captain Walker and marries him, but she does not actually speak or sing.
In this scene, the nurses sing “It’s a boy, Mrs. Walker”.
Kim joins the nurses around her when they sing “A son”.
Lyrics
Nurse: It’s a boy, Mrs. Walker, it’s a boy
It’s a boy, Mrs. Walker, it’s a boy
Kim & nurses: A son! A son! A son!