New Zealand's prime minister is pregnant, and that's a big deal for working mothers

New Zealand Prime Minister Jacinda Ardern is having a baby.

Ardern made the announcement via Twitter on Friday morning, writing that she and her partner Clarke Gayford will "join the many parents who wear two hats."

SEE ALSO: Why everyone's talking about New Zealand's next Prime Minister Jacinda Ardern

"I'll be PM & a mum while Clarke will be 'first man of fishing' & stay at home dad. There will be lots of questions (I can assure you we have a plan all ready to go!) but for now bring on 2018," she added.

The announcement makes Ardern the second woman ever to give birth while in office in modern government. 

Ardern follows in the footsteps of the late Benazir Bhutto, who as prime minister of Pakistan gave birth to her eldest daughter Bakhtawar Bhutto Zardari in 1990.

How the arrangement will work

When Ardern gives birth she will temporarily hand over her duties as prime minister. New Zealand has 18 weeks of parental leave, which is shared between mother and partner.

"We're both really happy. We wanted a family but weren't sure it would happen for us, which has made this news unexpected but exciting," Ardern said in a statement to Mashable. 

"Yesterday I met with Deputy Prime Minister, Winston Peters, to share the news and to ask him to take on the role of Acting Prime Minister for a period of 6 weeks after our baby is born," the statement added.

"As is the case when I am overseas, Mr Peters will act as Prime Minister, working with my office while staying in touch with me. I fully intend to be contactable and available throughout the six week period when needed."

At the end of Ardern's leave she will resume all prime ministerial duties, and Gayford will stay at home to care for their child.

"Clarke and I are privileged to be in the position where Clarke can stay home to be our primary caregiver. Knowing that so many parents juggle the care of their new babies, we consider ourselves to be very lucky," the statement added.

"We consider ourselves lucky for another reason. Clarke and I have always been clear we wanted to be parents but had been told we would need help for that to happen. That's made this news a fantastic surprise."

"We first knew of my pregnancy on the 13th of October, but as many couples do in the early stages, we kept it to ourselves. From a personal perspective, I am so looking forward to my new role as a parent. But I am equally focused on my job and responsibilities as Prime Minister."

It's a big deal for working mothers

Days after her appointment as the leader of the Labour Party last August, Ardern faced repeated questions about balancing a baby and her career. She didn't take that line of questioning lightly.

"For other women, it is totally unacceptable in 2017 to say women should have to answer that question in the workplace," she told the AM Show at the time.

"It is a woman's decision about when they choose to have children. It should not predetermine when they are given a job or are given opportunities."

Women have long had to deal with people doubting their ability to do their jobs competently while pregnant, while other women face discrimination from employers because they might *someday* have a baby.

We're sure Ardern will be just fine, thank you very much. And she seems pretty confident, too. 

"I am not the first woman to multitask," she told TV reporters. "I'm not the first woman to work and have a baby. I know these are special circumstances, but there will be many women who will have done this well before I have ... I'm excited. We're excited. We know together that we're going do make this work and New Zealand is going to help us raise our first child."

WATCH: Never lose your dog again with the help of this tracker