The couple is expecting a baby girl, a source tells PEOPLE.
Grey's Anatomy star Dane, 37, and Gayheart, 38, shared their good news in September by stepping out once the actress began to show, but never formally announced the pregnancy.
The couple were married in a 2004 Vegas wedding.
News of the Gayheart-Dane baby's gender was first reported by E! Online's Marc Malkin.