Lauren Conrad experienced fireworks on the Fourth of July when she went into labor with her first baby the night of her annual party


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Lauren Conrad certainly experienced fireworks on the Fourth of July.

The lifestyle expert, 31, went into labor with her first child 15 minutes after guests departed her and husband William Tell‘s annual July 4th party.

“Two days before, I said to William, I don’t think he’s coming before,” Conrad tells PEOPLE in this week’s issue. “I said, I think I’m going to be fine. I really would like to have a Fourth of July party. It’s my favorite day of the year. I love Fourth of July. I have this party every year.”

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Credit: Elizabeth Messina

While she says “no one believed me that I was going to do it,” the festivities continued with hot dogs, Mexican corn and minimal décor.

“We did it a little more low maintenance than we normally do,” the fashion designer explains. “We normally hand make all the hamburger patties and I do the La Scala chopped salad. But this year we barbecued, hung out and watched fireworks. We had maybe 30 people.”

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After watching fireworks on the beach — where Conrad didn’t wear a bathing suit “because I was just so pregnant” — the Hills alum headed to bed, leaving Tell, 37, to say goodbye to the guests.

“I felt so bad because it was such a long day,” Conrad says. “William came in an hour later, and as soon as his head hit the pillow, my water broke.”


RELATED VIDEO: Baby Boy on the Way for Lauren Conrad

The California couple, married since September 2014, hurried to the hospital where baby Liam James arrived July 5.

“They say that over holidays there are a lot of people in labor because you might ignore early symptoms,” continues Conrad, who says four moms-to-be arrived at the hospital just after her. “I think it’s the fireworks.”

For more on Lauren Conrad’s life as a new mom with husband William and son Liam, pick up this week’s issue of PEOPLE, on newsstands Friday.