The Trooper actress gave birth to daughter Lucia in Los Angeles on Thursday, reports US Weekly.
The couple are already parents to 7-year-old daughter Mattea, 5-year-old son Johnny and 2-year-old son Holden.
Sorvino performed her own stunts in Covert One: The Hades Factor while pregnant with Johnny.
The 44-year-old has insisted that family comes first and she always considers them before signing on for film roles.
In February 2011, police arrested Backus in San Francisco after an argument with Sorvino at a hotel.