Kim's Top Secret Plan About Her Pregnancy Weight Gain—Why The Kardashian Won't Have To Work So Hard To Lose It Post-Birth!

To avoid a similar struggle after having baby number two, Kim is determined to stay as slim as possible up until her December due date and has been working with celebrity trainer Harley Pasternak to keep her weight under control.

Star previously reported that doctors are concerned about Kim's drastic weight gain during her second pregnancy that could cause complications, even the risk of having to remove her uterus immediately after she gives birth.

"You can do most exercises that you would normally do while pregnant, you just can't do stuff on your back or too much abdominal work," Pasternak tells OK! "Kim often uses a Helix Lateral Trainer—it's like a lateral elliptical. It's popular with female clients because they can tone their butts and abductors and glutes in a lateral way."

Pasternak tries to accommodate Kim's busy lifestyle with bite-size workouts that don't require braving the paparazzi with a trip to the gym. "I'll send a video clip that says, 'Today you're going to do a reverse lunge... four sets of 25 repetitions.'"

To help Kim resist the urge to overeat, Pasternak reminds her that she needs only an extra 300 calories a day during pregnancy. And in the sweltering summer months in Calabasas, Calif., (or while she was on her vacay in St. Barts) he preaches the need for her to stay hydrated, which apparently isn't a problem. As Pasternak explains, "Kim guzzles tons of water!" Bottoms up, KK!