"Doria has not been officially invited," a Kensington Palace insider told the US tabloid.
"She won't be there."
The insider admits the lack of invitation is "definitely strange" - especially in light of the tough year the former actress has had with her estranged father, Thomas Markle.
It has also been reported that Doria will not be making a permanent move to London.
According to PEOPLE, Doria may have rooms set aside for her Harry and Meghan's new cottage, located close to the house where the couple's evening wedding party was held and where their engagement photos were taken about a year ago, but she’s not making a permanent move there.
In a statement released by Kensington Palace last month, Doria shared her reaction to her daughter's pregnancy.
“Ms. Ragland is very happy about this lovely news and she looks forward to welcoming her first grandchild,” the statement read.
Meghan and Harry, who are expecting their first child in 2019, will join Prince William, Kate Middleton and other members of the royal family in Norfolk for Christmas with the Queen at Sandringham.