The former Hills star, who turned 30 this year, announced the "amazing" news on her Twitter account and official website audrinapatridge.com.
Audrina Patridge (@AudrinaPatridge) December 18, 2015
In a picture she shared with her 2.4million Twitter followers, Audrina is flashing a huge smile as she holds up a Clear Blue pregnancy test!
The reality TV star, who is engaged to fiancé Corey Bohan, wrote in a tweet sponsored by Clear Blue: "I finally figured out what to get Corey for Christmas! #babyontheway #clearblueconfirmed #ad."
Writing a longer message on her official website, she continued: "I have some AMAZING news to share with you all! It has been incredibly difficult keeping my mouth shut on this one because all I've wanted to do is shout it from the rooftops!
"But, now that my doctor has given me the OK, it is safe to announce that…. I'm PREGGERS!!!:)."
Audrina, who shared news of her engagement on social media just four weeks ago, added: "It started with me not feeling too well - I didn't feel sick, but I definitely knew something was off between my mood swings and lack of energy.
"So, I took the test and TA-DA! I couldn't even believe my eyes. I called Corey upstairs to make sure I wasn't just seeing things and, well, let's just say that he had a permanent smile glued to his face for the rest of the night!"
The mum-to-be went on to reveal she is not suffering from morning sickness, but feels very tired and like she has "a major hangover when I wake up".
Audrina also told her fans they don't care what sex the baby is, saying: "As far as finding out the sex of the baby... We just want it to be healthy :) Girl or boy, we will be ecstatic either way!"
It will be the first child for Audrina and BMX biker Corey, 33, who have dated on/off for seven years.
The pair's first date was featured on an episode of The Hills, after Audrina split from bad boy Justin Brescia (aka Justin Bobby).
Corey proposed over a romantic dinner at the Summit House in Orange County, California.
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