Grammys Will Feature a Slow Beyonce

Beyonce is "very pregnant" -- according to a source with eyes on her as she prepares for her Grammys performance -- and the pace onstage will slow dramatically as a result.

Sources connected with the show tell TMZ, Beyonce is in rehearsals for Sunday's show but the routine is changing constantly and the word is she will not lock the performance in until Saturday night.

There will be an elaborate digital screen onstage, which we're told will create movement that will cover the slower pace onstage.

And there are other tricks ... we're told there will be cameos during Beyonce's performance.

One source says Beyonce has made it clear, "She'll be taking it easier than normal."