Sorvino and actor Christopher Backus married four years ago and are the parents of 4-year-old Mattea Angel and 2-year-old Johnny Christopher King.
"We are overjoyed at the thought of welcoming a new addition to the family," the 41-year-old, Oscar-winning actress told Us Weekly in an exclusive statement. "With each child, the love in our hearts has expanded beyond what we ever imagined was possible."
Sorvino won the Academy Award for her work in the 1995 Woody Allen comedy "Mighty Aphrodite." Her other film credits include "Quiz Show," "Romy and Michele's High School Reunion" and "At First Sight," and she was recently seen in the TV movie "The Last Templar" opposite Backus. Sorvino was also named a Goodwill Ambassador to combat Human Trafficking by the U.N. Office on Drugs and Crime Thursday.
Backus has appeared on the TV shows "The O.C." and "Will & Grace."