The Prime Minister's pregnancy is empowering for men as well as women, a New Zealand academic says.

Photo: RNZ / Rebekah Parsons-King

Prime Minister Jacinda Ardern announced yesterday she is pregnant and is due in June.

Winston Peters will take on the role of acting Prime Minister for six weeks after the baby is born, but Ms Ardern said she intends to be fully contactable and available over that period.

Massey University associate professor Grant Duncan said he applauds Ms Ardern's partner Clarke Gayford's decision to be a stay-at-home dad.

He said it was an opportunity for New Zealand to see that men could be primary carers.

"This is not only a great, empowering statement for women, but also for men.

"This will be an opportunity for us to reflect as a nation on men as carers ... men can be primary carer.

"And actually ... it's a really good thing ... we should give him the thumbs up for taking on that role."

Photo: RNZ / Rebekah Parsons-King

Prof Duncan said he was a stay-at-home dad himself and found it to be an enriching experience.

And while it was unusual for a head of state to take maternity leave, there were no constitutional issues for New Zealand, he said.

"I think that under no circumstances should we regard pregnancy or maternity as a disqualification or some kind of incapacitation for any kind of job.

"I think actually ... we should treat it as a really positive opportunity to make a really positive statement about gender equality and parenthood and family."

Professor Duncan said when in government, deputy Prime Minister Winston Peters was responsible and statesman-like - and he thought he would do well in the top job.

He said he has heard criticism that Ms Ardern should have told Mr Peters she was pregnant during coalition negotiations.

But Mr Peters knew when signing up as deputy Prime Minister that part of the job was to step into the role of acting Prime Minister if necessary, Prof Duncan said.

"Winston Peters is hardly in a position to complain about that."