....same story as below, this time from the slightly more reliable source New York gossip blog Page Six;
January 15, 2008 -- It looks like Victoria's Secret angel Alessandra Ambrosio won't be strutting down the runway in her skivvies anytime soon. The Brazilian beauty, 26, is pregnant with her first child. "She's a few months along," said our insider. Ambrosio is thrilled, she told pals at a weekend party at the Hollywood Hills house of her boyfriend, Jamie Mazur. Paris Hilton, sister Nicky and brother Barron all partied at the house after a night out at Teddy's.
And just to add fuel to the fire, two more articles, from OK Magazine and E! Online.
Although it still hasn't been confirmed by Alessandra's people I'm guessing the rumours are true - the sites that are reporting it now don't tend to mention anything unless they're about 95% certain of its reliability.