Paris Hilton shocked Christina Aguilera by declaring her the "most beautiful pregnant woman in the world" to a packed Las Vegas nightclub.The 'Dirrty' singer - who is yet to confirm rumours she is four months pregnant despite her visible bump - buried her head in husband Jordan Bratman's shoulder as the hotel heiress made the announcement at Las Vegas LAX Nightclub in the early hours of Sunday morning. Paris said: "Congratulations to the most beautiful pregnant woman in the world. You're gorgeous."A fellow guest at the party - hosted by Christina - said: "Christina was satin a VIP booth. She looked completely shocked for a moment and sank her head in Jordan's shoulder. But then they both just started laughing as everyone applauded."Earlier in the evening, Paris had been spotted putting her hand on Christina's stomach while the pair giggled.Other guests at the party included Spice Girl Mel B and magician Criss Angel.