Wales-born Christian and his wife Sibi, 44, who are already parents to eight-year-old daughter Emmeline, have confirmed that they are expecting their second child.
"They are truly a supportive couple, he [Christian] and Sibi are thrilled," a source told Us Weekly. "She's been traveling with him while he's been touring around for American Hustle."
Christian and Sibi at the Oscars 2014
Fans had speculated that Sibi was pregnant when she accompanied 40-year-old Christian to the Oscars on 2 March.
Supporting her husband, who was nominated for the Best Actor award, Sibi showed off the beginnings of a baby bump in a form-fitting black gown.
Christian and Sibi, whose real name is Sandra Blažić, married on 29 January 2000.
The Chicago-born brunette was formerly a model and make-up artist and also worked as a personal assistant to actress Winona Ryder, who starred alongside Christian in the 1994 version of Little Women.
Christian and Sibi welcomed their first baby on 27 March 2005 in Santa Monica, close to the Los Angeles home they have lived in for more than ten years.
The couple at the Critics Choice Awards in 2011
In 2010 Christian told Esquire magazine how much fatherhood had changed him.
"I find myself tearing up at the most ridiculous things now," he said. "Sitting next to my daughter while she's watching a movie, me and my wife look across at each other like, 'Oh my God! Are we really doing this? Yes we are!'"
"The last few years of my life have been spent just watching animation - for my daughter - and getting a kick out of that," he added. "I love anything that she likes. If she's getting a kick out of it, I love it."