Heidi Montag cried during her first ultrasound.

Heidi Montag and Spencer Pratt

Heidi Montag and Spencer Pratt

The 30-year-old reality TV star and her husband Spencer Pratt, 33, have revealed that they are expecting their first baby together and Spencer filmed a video of Heidi getting emotional when they saw their baby for the first time during a scan.

In the video, a tearful Heidi can be heard saying: "Oh my gosh. Oh my gosh! It's so big. I can't believe that's ours! That's so exciting!"

Spencer said Heidi has been broody for years but they waited to start a family until they were both ready.

Heidi explained to Us Weekly: "It might never be the perfect time, so we said, Let's move forward. We had all these conversations. We're older, we have more life experience. Nothing is holding us back.

"I wanted a baby three years ago. Spencer was a little hesitant. Then one thing after another came up. We had work obligations, like 'Celebrity Big Brother' in the UK, which I did not want to be pregnant for. I'm actually really thankful we waited. I thought I was ready in my twenties, but with everything we had going on, it just wouldn't have been a good situation for us.

"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 see I don't know anything."

Spencer added: "I think I'm ready. I know Heidi is ready!"

Heidi is currently 12 weeks pregnant and the couple's baby is due on October 19.