"Welcome my son, can't wait to show you around this crazy place," Ambrosio's fiancé Jamie Mazur tweeted on Monday. The name of the newborn has not yet been revealed.
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The 30-year-old Victoria's Secret model gave birth just two day after her baby shower. "So much fun at my little boy baby shower! Now just have to wait for him to arrive!" Ambrosio tweeted on Saturday.
Ambrosio and Mazur are already parents to 3-year-old daughter Anja.