Ardern 'can do both' - Jenny Shipley

Politicians from at home and abroad are reaching out to offer congratulations to Prime Minister Jacinda Ardern at hearing she is pregnant.

Ms Ardern, who became Prime Minister in October, announced this morning she and partner Clarke Gayford were expecting a baby in June.

Former prime minister Helen Clark was among the first to congratulate her, tweeting that it was going to be a "super busy year" with "much to look forward to".

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"Every #woman should have the choice of combining family & career," she said.

Australian Prime Minister Malcolm Turnbull also offered his congratulations on Twitter.

He said that when he spoke with Ms Ardern this morning she sounded more excited than she did when she won the election.

Opposition leader of the National Party Bill English said he and wife Mary wished Ms Ardern and her partner Clarke Gayford the very best.

He said it was an incredible privilege to be a parent and a new child would bring real joy to their lives.

The Green Party, which has a confidence and supply agreement with the Labour-led government, also congratulated Ms Ardern.

"That a woman can be the Prime Minister of New Zealand and choose to have a family while in office says a lot about the kind of country we are and that we can be - modern, progressive, inclusive, and equal," said Green Party Co-leader James Shaw.

"For that reason I know this announcement will be significant for many women, in particular, and that all New Zealanders will share in the Prime Minister's joy today."

'Many many families do this every day in New Zealand' - Dame Jenny Shipley

Former prime minister Jenny Shipley said it was brilliant news and she heartily congratulated the couple.

"A wonderful choice of our outstanding young woman leader who is also going to choose to be a parent. It will bring special insight, I suspect, in her work and joy to her family."

Dame Jenny said it made the job demanding in so far as you needed a "village". That had been the case when she had children, albeit older, when she was prime minister. And her husband Burton was ahead of his time, in the way he stepped up.

She said Ms Ardern would be fine in juggling parental and leadership responsibilities.

"She can do both, and frankly it's wonderful to see that we've got diversity in the parliament and a third woman Prime minister who is young and still in her childbearing years.

"Many many families do this every day in New Zealand. With big jobs, and every job is an important job in this economy. Jacinda happens to be Prime Minister and I have no doubt she'll surround herself with gifted and caring people.

"She'll also surround herself with smart people who'll help her do her job and I think it's another, a groundbreaking example of what women can do. We have women and men leading this country and we have women and men making choices. How lucky are we."

She said it was not the slightest bit relevant that Ardern may have known she was pregnant while negotiating the coalition agreement.

"If she knew while she was negotiating it should not have made a blind bit of difference to the outcome of those discussions and I think people need to be very careful not to delve into the personal lives of leaders in areas that are absolutely irrelevant to the successful governence of this country.

Good for women, great for politics, also good for New Zealand - Dame Annette King

Former Labour party deputy leader Annette King said the couple would make great parents, it was great for them personally and for the country.

"Jacinda has wanted to have children for as long as I've known her, she's just a natural with babies, they're a magnet to her so wherever we went if there was a baby that baby got the attention first.

"Also I think it's good for women, I think it's great for politics, and I think it's also good for New Zealand because once again here we are showing that you can do things differently in a country like ours."

Dame Annette said she did not know Ms Ardern was pregnant during negotiations.

"You would not have picked from her professional approach to what she was doing that this was also in her mind.

"I think what Jacinda talks to Winston about is her business, but she certainly told to him yesterday as she said and set out the plan to him. I think Winston is a man who would welcome her having a baby, he'd welcome a family and he'd know it was her business.

"It shows the generationship that we've got, not only in politics but in our approach to life in New Zealand.

"When I got into Parliament I was a sole parent of a 14-year-old child and what got me through was the support of family and friends.

"Jacinda's going to have family, friends and she's also got Clarke, who as she said is going to be a stay at home dad and that is something that she has believed in for a long time that both parents should have a role in bringing up children.

"And I think that's one of the big shifts where dads these days are far more involved than they were back in the day when I had a child."

Another former Prime Minister Sir Geoffrey Palmer said it was great to see a person could be prime minister and have a baby.

He says politicians should be in lockstep with the views of the people.

"People go through parenthood, they have babies and it does keep a politician grounded I think to go through the things that ordinary people go through.

"To some politicians live in a bubble, which is artificial, and this certainly will avoid that tendency."

Labour told before announcement

The Labour Party caucus was told about the pregnancy this morning, before Ms Ardern publicly announced the news on Instagram.

New MP Kiri Allan and her partner have a five-month-old baby girl who spends a lot of time in Parliament with her.

"Earlier today she let all the caucus know and I must say we are extremely, extremely delighted."

Ms Allan has a 5-month-old daughter who spends a lot of time in Parliament with her, and said it's important to have good support.

"Have a good crew around you, myself and Willow Jean's offices are next door to each other, it has a lot of whānau in there all the time making sure the kids are fed, dressed, bounced and walked and all the other things they need."

Another bit of advice she had for her leader was to enjoy the journey.

"Just enjoy it, it's the most fantastic thing ever, it's an honour and privilege to be a māmā."

Ms Allan said she knew it would be business as usual for the Prime Minister.

"There are so many working māmā out there, we all have the capacity to get on and do it, I know with Jacinda it's going to be an incredible delight and everything that comes with parenthood but also business as usual in some regards and she'll just get on doing the do."

Kiri Allan and her wife spent time with the Prime Minister over the holidays.

"My wife Natalie and I were discussing that once we found out, and now and then there were certainly signs. She had the glow."

Departments weigh in

Various government departments and ministries also had some timely advice for parents-to-be.