Pregnant Kim Kardashian -- Mama's Working Out for 2

Forget Lamaze classes -- Kim Kardashian's fetus is already getting its daily workout ... at the gym.

Kim -- who's roughly 3 months pregnant with Kanye West's baby -- took her barely-visible baby bump out for a cardio sesh this morning in L.A.

From the looks of it ... Kim's taking a page out of Jessica Simpson's maternity wardrobe playbook -- lots and lots of black clothing.

But we'll give her credit for the spandex. Then again ... she's only 12 weeks into this.