"Thanks for all your warm wishes. We are very happy. I'm gonna be a mama!" Wood tweeted Friday, before adding, "Song of the day. 'Sweet child of mine' #gunsandroses"
Wood, 25, and Bell, 26, met in 2005 on the set of the Green Day video for "Wake Me Up When September Ends," in which they both starred. They dated for about year before breaking up and then reuniting in 2011. In the interim, Wood dated and was engaged briefly to Marilyn Manson.