Maria Shriver won't let Katherine Schwarzenegger and Chris Pratt's baby call her ''grandma''.

The 64-year-old journalist will become a grandmother when her daughter Katherine - whom she has with her ex-husband Arnold Schwarzenegger - gives birth to the tot she's expecting with her husband Chris.

But Maria has shunned the term ''grandma'', as she would much rather come up with her own adorable nickname for the impending arrival to use.

She said: ''I'm not embracing that name exactly. I'm gonna come up with my own name. I'll just be Mama. No, I can't do that. I've got to do something else. I'll think of it. I'll figure it out.''

Although she's not thrilled about being called ''grandma'', Maria couldn't be happier for her daughter and the 'Guardians of the Galaxy' star.

She added to 'Entertainment Tonight': ''I'm really proud of her. Obviously, she and Chris are super happy. They're a blessing to each other.''

Meanwhile, Maria recently spoke about the upcoming addition to the family whilst speaking to Katherine, 30, Chris, 40, and her son Patrick Schwarzenegger on Instagram Live.

During the livestream, Chris - who already has seven-year-old son Jack with his ex-wife Anna Faris - spoke of his joy at joining their ''gorgeous family'', and the NBC anchor admitted she's looking forward to them making it bigger.

Chris praised Maria and Patrick's 'HomeTogether' show, as he said: ''I really love what you're doing.

''This is really fun, and being right here, right now, it's just uncanny, you guys are both just so beautiful.

''I'm so lucky to have married into such a gorgeous family.''

And Maria pointed out there is another special addition to the family on the way.

She added: ''You're gonna have another beautiful family member.''

Katherine's father Arnold has Schwarzenegger also spoke about the prospect of his daughter starting a family with Chris as he said he is ''looking forward'' to becoming a grandfather, but isn't ''pushing'' the pair to have kids.

He previously explained: ''I don't push it because I know it's going to happen eventually. It's up to Chris and her when they want to do that but I'm looking forward it to, yes.''