When Jessica Simpson tunes in for the premiere of NBC's Fashion Star March 13, her body won't look anything like it does now.

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"I wasn't pregnant when we shot it. It will be amazing to see myself with a waistline," the 31-year-old said during a conference call Thursday. "I'll be like a big blob sitting on the couch watching myself thin."

Simpson will mentor 14 contestants alongside fellow fashion designers Nicole Richie, 30, and John Varvatos; supermodel Elle Macpherson, 47, will host.

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"Teaming up with this show was a perfect fit," Simpson said. "I couldn't turn it down because I felt like it was great for my collection, but it was also important for me to talk to these up-and-coming designers and mentor them and kind of show them the ropes and really try to lead them in the right direction."

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Now that she's expecting her first child with fiance Eric Johnson, Simpson said she's thinking of creating a maternity line for the Jessica Simpson Collection.

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"The point of launching a maternity line, for me, is to do something different," Simpson explained. "I'm not buying any maternity clothes. I'm wearing all clothes that come in bigger sizes. I really want to make a maternity line that's comfortable, but really stylish for people, because I believe that we all deserve to feel good and look good."

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