The 41-year-old actress had her first child, son Billy Ray, with Burton in 2003.
Carter recently starred in "Harry Potter and the Order of The Phoenix" as Bellatrix Lestrange.
According to the entertainment Web site IMDB, she is working on three other films, including "Sweeney Todd: The Demon Barber of Fleet Street," which Burton is directing.
Photos: Baby Bumps
Carter plays Mrs. Lovett in the film in which Johnny Depp stars.
Burton won an Oscar in 2005 for directing the animated film "Corpse Bride."