Jessica Simpson on Her Big Baby Bump: It's Not Twins!

Jessica Simpson has one of the biggest baby bumps in Hollywood -- leading some to believe she's got an extra bun in the oven.

During an appearance on "The Tonight Show With Jay Leno" on Monday, the 31-year-old "Fashion Star" mentor finally put rumors to rest. "No, it's not twins," Simpson said. "I know it looks like it."

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When Jay Leno, 61, joked that Simpson looked like she might give birth any minute, she replied: "Not quite yet. We have some time."

Adding that she's "waddling at this point," Simpson pointed out that she was wearing sky-high heels. "It's a lot of weight to carry on six inches!"

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Simpson, who is expecting a baby girl with fiance Eric Johnson this spring, admitted she's nervous about giving birth. "Labor is really going to hurt," she told Leno. "I have so much respect for my mom and all the women across the world."

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The pregnant star also explained why she and Johnson, 32, have yet to tie the knot. "I want him to be my husband so bad," she laughed. "I do still want to wear the pretty gown, so I have to wait."

Simpson then pointed to her belly an added: "Now she'll just be in the wedding."

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