The supermodel, who's expecting her fourth child with her husband, Seal, in October, returns to TV Thursday on Project Runway (10 p.m. ET/PT). The show has changed networks — from Bravo to Lifetime TV — but Klum says not to expect major changes in the series as it starts Season 6.

"Lifetime bought a show that they loved. They didn't buy a show to change it; they bought it to bring the show to their audience," she says. "I was kind of into changing a few things: the colors a little bit, changing the set a little bit or maybe making the runway a little bit different. But they liked it as it was."

The show gives 16 aspiring fashion designers a shot at showing their line at New York Fashion Week.

Tim Gunn returns as the contestants' mentor, and fashion editor Nina Garcia and designer Michael Kors return as judges.

This season, the show is based in Los Angeles, not New York like previous seasons, because Klum said she and producers wanted to give the show a fresh viewpoint.

Immediately after the show each week, viewers can watch a half-hour companion show, Models of the Runway (11 p.m. ET/PT),which goes behind the scenes with the Project Runway models.

Klum says she developed the idea with the show's producers.

"All these years ... there were all these great and funny moments that happened between the models and the designers. Last-minute things that were happening, like where they sew a girl into the clothes and she can't go pee anymore or she can't sit," Klum says, laughing.

This year's diverse collection of contestants will perform the most over-the-top fashion challenges in the series so far, Klum says.

"People love this show because we always come up with great new challenges, and we always have great talented people," she says. "People want to see what these designers have to do next and if they can do it. I don't think people watch our show because of who is going out with who on the show or who is the bitchiest. Those things do happen, though!"

Project Runway: All-Star Challenge will air before tonight's premiere (8 ET/PT). Eight contestants from previous seasons compete in the two-hour special to win $100,000. Nicole Kidman will be a guest on the show.