Her co-host on MIX 106.3, Nige thought he was simply taking part in a photo shoot earlier this week. But, when the photographer went to take the shot, Kristen said, 'OK, one, two, three, Kristen's pregnant".

"Nige stood there, not saying anything and you could see him trying to process it, his mind ticking over," Kristen said, in an interview this week with husband Iain by her side in their chic Kingston apartment.

"He hugged me and said, 'I'm going to be an uncle?' and I said, 'Yes'. And then he said, 'I've just got one request. Can I please teach your baby to drive? That would be such an honour.

"And I said, 'Suuuure, yes." And then she laughs. Life is good right now.

Kristen says it was time to make an announcement with her bump coming along nicely. And after the zipper on one outfit broke as she was leaving for a cocktail party last week.

She is also due to host fashions on the field at the Black Opal on Sunday in a pretty tight outfit. And even a kindly woman at her local Woollies asked Kristen, with a conspiratorial glint in her eye, if she was "patting her belly".

"Every morning we ask our listeners to share their lives with us so I'm just so happy to share part of my life with them too. Although, it's not lost on me I'm not the first woman to have a baby and I won't be talking about this for three hours every morning," she said, with a laugh.

The baby is due in August. Kristen and Iain are choosing not to find out the gender until the birth.

"It's helped me to be really present, not think about names and gender," she said.

"There are not many times when you're an adult that you get a real surprise. And what a beautiful surprise. Whoever is meant to come to you is meant to come to you."

It wasn't all plain sailing. While Kristen and Iain had no problems with fertility, they did do blood tracking at Compass Fertility in Canberra when they tried to get pregnant for six months without success.

Kristen, 36, wanted to get things moving, worried not so much about this pregnancy, but having enough time down the track for "baby No.2 or baby No. 3".

"Once you hear that description, 'geriatric mother', you think, 'Oh, shit'," she said, referring to the medical term for pregnant women aged over 35.

For two months, the couple did the blood tracking, which pinpoints ovulation and the optimal time to have sex. From there, Kristen became pregnant almost straight away.

"it does kind of take the romance out of it," she said. "You have a blood test and they send you a text, 'Hi Kristen, please have intercourse on *date* and please have intercourse on *date* and come back for another blood test on *date*'."

But the experience did give her a taste of the struggles so many people have in getting pregnant. She said the waiting room where women, with or without partners, waited for their blood test, perhaps the one that would tell them they were pregnant or not, was heavy with expectation. And longing.

"It's silent, no one talks to anyone. You see some people come back. You never see others again. But it's this weird camaraderie," she said.

Kristen took her own pregnancy test by herself at home the day before her planned pregnancy blood test at Compass. She didn't feel pregnant and was not expecting a positive result.

"It was nice. A moment to connect. It was like, 'OK, I think we might be on here'," she said.

It was December and the height of Christmas party season. Iain, who is a national director Colliers International, rushed in at the end of the day to change for a party as Kristen was busting to share the good news with him.

"He put a pie in the microwave and I thought, 'I'll just let him finish his pie before I tell him, let him have that moment before everything changes," she said.

"We'll always remember that day because that was the day everything changed."

Iain, 35, is thrilled. He went with Kristen on Wednesday for her scan and heard the baby's heartbeat for the first time. It was "magical".

He said it was a new adventure after their memorable wedding in New Zealand in May last year.

Iain has always been a planner and he's still planning for life after the baby.

"From 12 weeks, it started to get real. It was, 'OK, cool, we're out of the danger zone now'. So you invest in it emotionally and think, 'OK, I need to start planning our lives for when the baby comes'. But then you realise it's due in August and it's now March," he said, with a laugh.

Iain's twin sister Aimee is also pregnant, due in four weeks. He is one of four children. Kristen has her sister Nikkee, who she confided in early in her pregnancy. And, no, Kristen is not expecting twins.

It's a measure of how close Kristen and Nige are that he was one of only two people at the station (the other was their producer Tamara Cartwright) who knew she was trying to get pregnant and getting help with blood tracking. The blood tests were at the clinic early in the morning, not ideal for a breakfast radio host, who was on air on the time.

So Nige would cover for Kristen as she slipped out during the last ad break of the program to rush to the clinic to get the test done.

"He's better in these situations than he ever gives himself credit for," Kristen said.

"He has been the person who has asked the most questions and been the most interested."

But Nige still never cottoned on that she was actually pregnant.

"I'd been wearing this A-line dress to work to cover it up. When I finally told him I was pregnant, Nige was like, 'Thank God, because I was sick of seeing that dress'," she said.

Nige, who does not have children, is likely to be the ultimate favourite uncle to Iain and Kristen's child.

But they have knocked back his offer for an "epic gender reveal". He wanted to blow out pink or blue smoke doing a burn-out.

In all seriousness, Kristen says the Kristen and Nige show will continue after the baby arrives.

She will have the baby in the last week of the last ratings period for the season. Seriously.

"People at work were saying, 'Only you could have done that'. But it was through good luck rather than good management," she said.

Nige and Kristen will both have a break at the end of the year and the show will return in early 2021.

"I've always been career-driven. I've got my vision board, my goals board," Kristen said.

"Having a baby is something I've always really wanted but now everything is out of your control. I just have to keep healthy and trust my body that it knows what to do."