Definitely keep her conditioned well, whether it is working her on the ground, or riding.
The better shape she stays in, the easier the foaling will be on her, and the quicker she'll bounce back.
I rode my pregnant mare all summer and fall (of course she did not have any "stress" issues either). Quit once winter came and we had tons of snow....
The following spring she was sooo big, and just looked miserable, so I would never have even tried to ride her.
But I got lots of comments on how great she looked.
Foaling went well, and she got her "girlish figure" back in no time.
I started riding her again when her colt was three weeks old, but just very short ones so that Kizmit could follow along, as soon as he looked like he was ready for a nap or suckle we were done.
Enjoy that new baby when it arrives! They are just so precious, and grow up much too quickly......