Richards, 34, is six months pregnant with the couple's second child. They also have a daughter, Sam, who will be a year old next week.
The couple married in June 2002 and co-starred in "Scary Movie 3." Richards and Sheen, 39, met while shooting the independent film "Good Advice" in 2000.
They began dating after Richards guest-starred on Sheen's former series "Spin City." The marriage was Sheen's second and Richards' first.
Sheen, who now stars in the CBS sitcom "Two and a Half Men," is best known for his work in the movies "Platoon," "Ferris Bueller's Day Off" and "Hot Shots."
Richards, a former Bond girl, has appeared in a host of movies, including "Wild Things" and "Starship Troopers."