The Transformers star stunned onlookers on Monday night (11Apr16) when she arrived at a CinemaCon event in Las Vegas to promote Teenage Mutant Ninja Turtles: Out of the Shadows with a noticeable baby bump

She later confirmed that reports of her pregnancy were true, telling all about the difficulties she faced filming the action movie last year (15).

But the one mystery Megan, 29, did not provide an answer to was the paternity of her unborn child. The brunette beauty filed for divorce from actor Brian Austin Green in August (15), ending an 11-year romance and a five-year marriage.

She cited "irreconcilable differences" and requested joint physical and legal custody of the couple's two sons, Noah, three, and Bodhi, two. And while she and Brian have been spotted out and about with their kids since announcing the split, the pair's divorce has yet to be finalised, prompting many fans to suggest Brian is the baby daddy. Others felt sure one of her recent male co-stars could be the father.

On Tuesday (12Apr16), Megan took to and slyly responded to the gossip by posting a photo collage of herself next to three of her past and present male co-stars - Transformers' Shia LaBeouf, Teenage Mutant Ninja Turtles actor Will Arnett, and Jake Johnson, her onscreen love interest during her recent guest arc on U.S. sitcom New Girl.

She simply wrote the caption, "#NotTheFather".

Multiple sources tell E! News Brian is the dad, and divorce proceedings are reportedly going to "be put on hold for a while" due to her pregnancy.

The insider adds, "This pregnancy was not planned, but when they found out they were extremely happy."