A source on the Gossip Girl set revealed to Page Six that Lively has been practically "glowing" and indulging in more food than usual since filming commenced.
"Blake is usually really careful about what she eats, but since her wedding, she seems to be eating a lot more. Everyone on set is on bump-watch," the insider claimed.
Lively and Reynolds have not responded to the pregnancy rumour.
The couple tied the knot earlier this month at Boone Hall Plantation at Mount Pleasant, near Charleston in South Carolina, in front of family and friends including Florence Welch.
Reynolds and Lively started dating in October 2011 after the actor's divorce from Scarlett Johansson was finalised.
They also starred together in the superhero epic Green Lantern last year.
Watch a Green Lantern trailer below: