Jamie McCarthy/WireImage.com 1 / 8
Jamie McCarthy/WireImage.com 1 / 8

USMagazine -- Jessica Simpson, 31, confirmed last month that she and fiance Eric Johnson were expecting their first child, but the "Fashion Star" mentor tells Us Weekly she and Johnson won't be saying "I do" until after the baby is born.

"We were always going to wait [until] after the baby" she explained. "We flirted around with different dates before I found out I was pregnant, and thankfully we didn't lock anything down. I want to enjoy the day… I'm glad we didn't make a deposit."

"I just didn't want to be stressed out," said Simpson, who got engaged to Johnson in Nov. 2010. "Now when I get stressed out it's like 50 times worse. So I really want to enjoy that day and now I get to have my baby with me."

After months of speculation, Simpson announced her pregnancy on Halloween with a visual pun. She posted a picture of herself dressed as a mummy on JessicaSimpson.com with the caption, "It's true, I'm going to be a mummy!"

"My kid's going to think I'm pretty cool," she told Us about the announcement. "This is a cool thing to welcome him to the world with."

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