Kristin Cavallari and Jay Cutler are "almost giddy" with excitement about her pregnancy.

The reality TV star and her football player fianc announced they are expecting their first child on Sunday.

The pair's relationship has been on/off, but they confirmed they were back together and engaged again late last year. Although they are starting a family quickly, both couldn't be happier about impending parenthood.

A source told Chicago Sun-Times the pair are "almost giddy" with joy about their unborn baby.

"A lot of people might be surprised to hear this, but Jay is really looking forward to becoming a dad He's a very private guy and often curt with the press, but privately he is very much a big teddy bear," the insider added.

The pair are now considering when the best time to tie the knot might be. They may decide to wed before Kristin's gives birth, although they don't feel any pressure to do so.

"So many couples have kids first and then marry afterward, there isn't the pressure to [get married] as much these days," the source explained.

Kristin, 25, has the full support of her family. Her mother Judith Spies is said to be particularly excited about the new arrival.

"She is thrilled by the news, as you would expect. But isn't that normally the case with all grandparents?" another source said.

Kristin and Jay got engaged last April after a whirlwind romance. They split in July, with Kristin then confirming the wedding was back on in November.