Pregnant Hilary Duff Hides Her Baby Bump At Pilates

Well, we got a peek at her belly when she went shopping on Thursday, so it's not like she's trying to keep her pregnancy totally under wraps!

Hilary Duff was photographed arriving at her Pilates class in Studio City on Friday afternoon, and the former Disney darling rocked a comfy pair of yoga pants and covered up her baby bump with a loose knit top.

So what exactly is the 23-year-old starlet doing during her gym sessions? Duff's trainer Harley Pasternak reveals that he keeps her “in a cool room” and pays close attention to her heart rate during workouts. “No impact, no hyper bouncing and plyometrics,” he recently told People. Duff sweats it out with Pasternak three to five times a week, and the duo focus on “low impact exercises” including incline heel walking, stairs and the elliptical machine.

Duff and husband Mike Comrie announced that they were expecting their first child together just last month, so she's got a ways to go before she's walking in January Jones' shoes...