Julie Anne Genter, Green Party minister and a candidate as co-leader, is pregnant.
She announced the news in a personal statement from her home in Auckland today. It follows a series of miscarriages, which she has spoken about previously.
The baby, with partner Peter Nunns, is due in the first week of August.
Genter also posted the news on Facebook.
"Peter and I have some amazing news! We're going to have to get an additional seat for the bikes - in the first week of August we're expecting our first child. 2018 is going to be an even bigger adventure!"
Genter said there was no reason for her to withdraw from the Green Party leadership contest.
She said she found out about the pregnancy in December: "Clearly there is something in the water at Bellamy's."
She said she had told Jacinda Ardern the same day she shared her baby news with the world, and informed co-leader James Shaw at the same time, but did not tell other Green MPs until last weekend.
This will be the first baby for Genter and Nunns.
Genter said she would probably work until the 37th week of her pregnancy, and would stay in Auckland for two months after the birth before returning to Parliament.
She said she would have the baby in the Parnell Birthing Centre because it was close to Auckland Hospital "in case anything goes wrong".
Nunns said it was good that men could see from his example, and that of Ardern's partner Clarke Gayford, that men staying at home to look after a baby was an option.
He said he did not know Gayford and had not talked to him about it, but added: "I think I'll get to know him."
Last year, Genter revealed in the Woman's Weekly she had suffered a series of miscarriages.
"I never expected we'd have any problem getting pregnant, in fact, I didn't," she told the magazine.
"But I lost the pregnancy very early on. And then the next one at eight weeks. We tried for another year after that, but nothing happened.
"I'm quite a rational person and thought I could tell myself it simply wasn't meant to be, but I was surprised at how intensely powerful my emotions were around the pregnancies and miscarriages. It affected me profoundly. It was upsetting and very sad for both of us."
Speaking in March, she said then she was considering adoption, but had her mind set on the upcoming election. People needed to discuss miscarriages more openly, she added.
"Maybe we don't mention it because we don't want other people to feel the sadness, but how else will women know how common it is and how will other people know what you're going through?"
Genter is Minister for Women, and is Associate Minister of Health and Transport - and is a candidate for the Greens co-leadership.
She has been a Green Party MP since 2011. She was born in and grew up in the United States and is a dual citizen of the US and New Zealand.
Nunns, also educated in the US, is an economist who has worked since 2014 for Australian-based transport consultancy MRCagney.
He was seconded to Auckland Council's Research, Investigations and Monitoring Unit from May 2014 to March 2015.
According to his LinkedIn profile, he previously worked for PricewaterhouseCoopers NZ from 2012 to 2014, and before that for the Ministry of Bushiness, Innovation and Employment from 2008 to 2011. He is an occasional commentator on the blog site Greater Auckland.
Genter lost to Ardern in the Mt Albert by-election last year but said she attended her victory party.
In her Woman's Day interview, she said: "I wanted to congratulate her in person because we're friends.
"She was really sweet and wanted to know how I felt. Our friendship is still very much intact – if anything, this has strengthened it."
At the time, Genter, Ardern and National's Nikki Kaye were the only women in Parliament under the age of 40 - a fact the pair had bonded over.
Genter had hosted Ardern and Gayford for a dinner party at her home in 2016.
In April, Genter revealed she received an email from a member of the public which appeared to blame her miscarriages on fluoride in the water supply.
The email, which she posted on Facebook, read: "I read in the paper a little while ago that you had two miscarriages. Therefore I thought I would send you this information on fluoride. People don't realise how toxic fluoride is, even at low levels.
"I presume that is because the dentists will be extremely embarrassed if it is found that they are wrong."
It adds that "more and more research" is being conducted, and there is "no need to have it in the water".
"Children need to be taught to brush their teeth and parents need to keep them off soft drinks."
Genter's rival in the Greens co-leadership contest is Marama Davidson, a mother of six who became an MP in 2015 after Russel Norman resigned from Parliament.
The women's leadership post was vacated by Metiria Turei before the September in the wake of fall-out from an admission she had made a false claims to Social Welfare when she was on the domestic purposes benefit.
The timeline for the contest set out by the Green Party is as follows:
Sat Mar 3: Co-leader candidate session at Green Party policy conference in Napier (open to media, details to be advised closer to the time)
Sun Mar 25: All delegates Zoom (video) call with Co-leader candidates. This will be a virtual version of what normally happens at AGM with Co-leader candidates giving speeches and answering questions from delegates
Mon Mar 26: End of official campaigning
Mon Mar 26 to Sat Apr 7: Branch consultation and delegates cast their ballots
Sat Apr 7: Balloting closes
Sun Apr 8: Ballot counting and winner announced