Organisers have confirmed that the Chicago star will perform a duet with co-star Queen Latifah.
There will be a medical team on standby at the Kodak Theatre in Hollywood in case she goes into labour during the event.
Catherine said: "Originally I wanted to high-kick my way through the number the way I do in the film but of course that's out of the question now.
"I'm just going to have to stand there and perform a few gentle moves.
"I very much wanted to do the song and hope - fingers crossed - everything will go well and I will be able to perform on Sunday."
According to The Sun, they will sing I Move On from the movie - which is up for 13 Academy Awards.
Catherine is expected to scoop Best Supporting Actress at the glittering awards ceremony for her role as Velma Kelly in Chicago.
She will be vying for the award with her singing partner on the night, Queen Latifah. Renee Zellweger is up for Best Actress for her role as killer Roxie Hart in the film.
