Washington, Feb 24 : Nicole Richie celebrated her second pregnancy at a post-Oscar party.

The socialite and her beau Joel Madden, who welcomed daughter Harlow in January 2008, stayed back till 4 a. m. at a private bash in the Hollywood Hills hosted by Rick Yorn, Patrick Whitesell, Mike Deluca and Brent Bolthouse.

"She looks very happy," Us magazine quoted a source as saying.

Prior to the Oscars ceremony, Madden announced on his blog that he and Richie were expecting their second child.

"What''s better than winning an Oscar? I am so happy to tell everyone that Harlow is going to be a big sister!" he wrote. (ANI)