The actor announced the happy news during an interview on U.S. Tv show Chelsea Lately on Wednesday (17Jul13).
He showed off a picture of his wife and crudely commented on the size of her breasts, saying, "Her breasts are very big these days. Would you like to know why? Cause I put a baby in her belly!"
The actor later retweeted a sonogram image of their unborn child, which Mollen had posted on Twitter.com.
The pair wed in April 2008 after meeting on the set of My Best Friend's Girl.