The 30-year-old reality star confirmed she's pregnant with a son in the May 22 issue of Us Weekly after announcing she's expecting with husband Spencer Pratt.
"I ran into the room and said, 'It's the doctor's office!'" Montag recalled. "The doctor said, 'It's a boy!' I started screaming."
"It was in my heart to have a boy," she confessed. "I thought Spencer really used to want a boy, and then a few months ago we had a conversation where he said, 'Let's just make sure it's healthy. Boy or girl, I don't care.'"
"I hope to have a little girl one day, but for my first child, I really wanted a son," the star said. "I thought it'd be a more natural bond for Spencer since he and his dad are so close."
Montag told her 1.5 million Twitter followers that she's "so excited about life" and becoming a mom. She celebrated her eighth wedding anniversary with Pratt on April 26 after sharing their baby news earlier in the month.
"Happy 8 year anniversary @spencerpratt!" the star wrote. "Thank you for the best gift... a baby. So excited to continue on this blessed journey together! Love you."
Montag came to fame on the MTV series Laguna Beach before starring with Pratt on The Hills. She showed off her baby bump in a photo from a relaxing day with Pratt last week.
"Sunday fun day.. the 3 of us," the star captioned the picture.
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