Sorvino told People magazine she is due in the summer.
Their daughter Mattea Angel was born in November 2004.
Sorvino, 38, and Backus, 24, met through a mutual friend in August 200, got engaged a month later and married in June 2004.
The daughter of actor Paul Sorvino won an Academy Award in 1995 for her role in Woody Allen's "Mighty Aphrodite."
She is nominated for a Golden Globe for her role in the Lifetime's "Human Trafficking" miniseries.
Backus recently finished shooting the poker film, "All In."