Ashlee Simpson is pregnant, a source confirmed to Us magazine.com. Simpson 23, is expecting her first child with fiancé Pete Wentz, 28.

Simpson and Wentz, the Fall Out Boy bassist announced their engagement last Wednesday. “They are ecstatic and can’t wait to be man and wife,” a source told Us. “They will be getting married before the end of the year.”

photos provided by PR Photos

Wentz, who co-founded Fall Out Boy in 2001, told Us this month that he was open to marriage.

Ashlee Simpson, 23 and her rocker boyfriend, Pete Wentz, 28 are getting married! Us magazine.com has confirmed.A rep for Simpson tells Us, “Yes, they are happily engaged.” Simpson and Wentz began dating in late 2006.

photo provided by PR Photos

“They are ecstatic and can’t wait to be man and wife,” a source tells Us. “They will be getting married before the end of the year.”