Megan Fox raised all sorts of questions Monday night ... flaunting what sure appears to be a baby bump. 

Megan hit up CinemaCon to promote the latest installment of 'Teenage Mutant Ninja Turtles,' but it was all overshadowed by what appears to be a deliberate pose to accentuate the protrusion. 

Megan has 2 sons -- Noah, 3, and Bodhi, 2 -- with estranged husband Brian Austin Green.

You'll recall, she filed for divorce back in August ... but they've been together a lot recently and seem tight.

Congrats?