Parliament's new parents Willow-Jean Prime and Kiri Allan pass on congratulations to PM and partner

Willow-Jean Prime is the latest MP to not only have a baby - but bring her along to a sitting of Parliament.

If Jacinda Ardern decides to take her newborn into Parliament after the child is born in June, it won't be the first time.

Labour list MP Prime has breastfed her daughter Heeni in the chamber.

Speaker Trevor Mallard was so smitten by seven-week-old, Heeni, he held her for part of the session in November.

Heeni didn't seem bothered by Mallard's attention and continued sleeping.

Prime has already shared her congratulations to Ardern and partner Clarke Gayford on social media this morning.

Ngā mihi Jacinda Ardern & Clarke ❤️❤️❤️ #auntiesareready #village #exciting

Posted by Willow-Jean Prime on Thursday, 18 January 2018

Fellow new Labour MP Kiritapu Allan has also taken her newborn along to a sitting.

She also shared her congratulations, labelling it "the best news ever".

Best news ever! A new sproglet to add to the growing sproglet contingent in Parly!! Perhaps there will be a sproglet caucus pretty soon 🤔🤔🤔

Posted by Kiri Allan on Thursday, 18 January 2018

This picture essentially sums up my year: thank you for the honour of representing our folk in Parliament, NZ - who would have thunk it, huh.

Posted by Kiri Allan on Saturday, 30 December 2017

Parliament of the 90s established a childcare centre while a special room was set up in the early 80s to help women breastfeed.

Back in 2002, then National MP Katherine Rich also breastfed her baby in Parliament.

When contacted today, Rich declined to comment about Ardern's announcement but through a spokesman issued her "warmest congratulations".

But it was former Labour MP and Ngai Tahu woman Whetu Tirikatene-Sullivan who was the first minister to become pregnant while in Parliament.

Tirikatene-Sullivan, who died in 2011, represented Southern Maori for Labour from 1967 to 1996.

She returned to Cabinet two weeks after giving birth.

Former National finance minister Ruth Richardson labelled Tirikatene-Sullivan as the glass-ceiling breaker for women in Parliament.

"There's an overwhelming observation which is New Zealand has dramatically modernised both its institutions and its attitudes since Whetu Tirikatene-Sullivan and myself were the first two to have children and be pregnant while we were parliamentarians.

"Whetu's children used to babysit mine, so was about 10 or so years ahead of me.

"So, Whetu broke the glass ceiling, as it were, originally."

Richardson said both of her children were born while she was a parliamentarian. Both had had children of their own in the last six months.

"And of course that's led me to reflect in the dramatic shift in expectations and attitudes that exist. There is now on the part of parents and expectation that they will make personal decisions free from external constraints or indeed prejudices and there's an expectation from the public that we need to celebrate the joy of a baby and be flexible in the way we accommodate the parents' wishes."

There had been a shift in not only views about a parliamentarian giving birth but also who would be the primary caregiver.

"When Andrew was the primary caregiver at home that was very different for a father at that stage and now nobody blinks an eyelid as to which parent will make that choice."

As for Ardern announcing she will step down for just six weeks after giving birth, Richardson said she could only take three weeks off.

"It all depends ... six weeks may be her choice but it may not be her body's choice or her baby's choice. You've just got to be, as the workforce, flexible enough for the demands a small infant will place on both of you."

Parenting was taxing but "you learn to juggle multiple responsibilities", she said.

"It's very cool to live in a country where this kind of news can break and people's attitude is 'good on them', and 'it's a thrill for them' and 'we want them to have the happiness that all parents have'."

Former Green MP Holly Walker has revealed the stress of juggling a first baby with her parliamentary career drove her to self-injury.

Walker, from Lower Hutt, left Parliament in 2014 after one term.

She compiled a candid memoir of the torturous period, titled "The Whole Intimate Mess" which covered post-natal anxiety, a chronically ill husband, and domestic unrest.

She suffered panic attacks and anxiety and also began striking herself during arguments with her husband Dave.

Walker, who is currently on maternity leave with their second child, passed on her regards to Ardern and Gayford through a spokesperson.

Meanwhile, across the ditch last year, Australian senator Larissa Waters made history when she breastfed her baby inside the Australian Parliament.

Ardern will not be the first woman to give birth while in office - almost 30 years ago the Prime Minister of Pakistan gave birth to her second child while in power.

Benazir Bhutto gave birth to her daughter Bakhtawar on January, 25 1990, and was reportedly the first modern head of government to give birth while in office.

Her first-born, Bilawal, was born on September 21, 1988, mere weeks before she took office in December 1988.

Her third child, Aseefa, was also a just a few months old when she assumed office for the second time in October 1993.

Ardern announced the news on Instagram this morning before a press conference outside her Pt Chevalier home.

She discovered she was pregnant on October 13 - just six days before she became Prime Minister-elect.

Winston Peters announced NZ First would form a coalition with Labour on October 19.