According to Star magazine and Radar Online, Bellizzi, 35, told her friends that Gibson is the father of her child.
Father to nine children already, three girls and six boys born from three previous marriages, Mel Gibson has fought for the custody of 1-year-old Lucia, his daughter born from his relationship with Oksana Grigorieva.
However, contacted by Radar, Laura Bellizzi and Mel Gibson’s reps have denied the actor’s paternity.
His rep dismissed the reports on Thursday as “complete and utter rubbish, 100 per cent untrue.”
According to sources, Bellizzi doesn’t want the news to go public but is telling her friends “that the Braveheart actor is the father of her unborn baby.”
“Laura’s being as secretive as she can be about it,” an insider told Star. “But she’s really showing now, and people are beginning to ask the question: “Who’s the daddy?””
In addition, a source close to Gibson says that it is “physically impossible” for the actor to have fathered the child.