Heidi Pratt is pregnant with her first child.

The 30-year-old reality TV star can't wait for her and husband Spencer Pratt to welcome their baby into the world later this year, and she's been doing as much as she can to prepare for the impending new arrival, having realised she ''doesn't know anything''.

Speaking to US Weekly magazine about the exciting news, the 'The Hills' alumni said: ''I have never been more excited. The reality is sinking in that we are going to have a child! I've read every pregnancy book, and now I realise I don't know anything.

''I wanted a baby three years ago. Spencer was a little hesitant.''

And her 33-year-old spouse won't forget the moment he was told he would be a father and he is equally as thrilled about their news.

Speaking about the moment he found out the news, he said: ''[Heidi was] just standing there. The look on her face, I can't even describe it. She was literally glowing. I thought she was about to say she made muffins or banana bread.

''Heidi said, 'I'm pregnant'. I was like, 'Whoa, that's way more exciting than banana bread!'

''Heidi has wanted to be a mom since the day I met her. She has planned for and thought about this.

''It's just the click-click-click of the roller coaster going up. That's how I feel right now.''

Heidi was amazed to fall pregnant within the first month of trying to start a family.

She explained: ''It happened the first month.

''I was so shocked; Spencer wasn't. He was so sure it would happen right away. He was like, ''You're going to get pregnant the first time we try.''

The blonde-haired beauty is currently 12 weeks pregnant and her expected due date is October 19, but she is currently suffering from ''really bad'' morning sickness.

She explained: ''I felt nauseous and I wanted to know, so I took a pregnancy test.

''I've had really bad morning sickness since the beginning, but I've never been so happy to feel so sick! Every time I feel awful, I remember why and I'm just euphoric. It's so fulfilling, and I'm mostly just grateful. I've been with the love of my life for 10 years, and now we're starting our own family.''