Jacinda Ardern is having a busy week. By early Friday afternoon she had launched a plastic bag ban, negotiated an end to a strike by nurses and announced plans for a new mental health hospital.

From the outside it appears to be business as usual for New Zealand’s prime minister. But seven weeks ago Ardern became only the second leader in the world to give birth while in office, and on Monday she returned to work having to juggle the responsibilities of office with the demands of parenthood.

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Some things have had to change. Among them is the prime minister’s office tea room, which has been converted into a baby changing room for Ardern’s daughter, Neve Te Aroha. Another is the working day, which now includes breastfeeding every three hours, sometimes mid-briefing. A third thing that has changed is Ardern’s perspective.

“Of course it is hard graft in those early weeks,” says Ardern, who appears as relaxed as ever as she speaks to the Guardian about her first weeks of motherhood.

“We’re still a very busy workplace obviously and there’s a lot going on, but you get these small moments where I will break to feed Neve and I will continue to be briefed while I am doing that, but it just means that probably the atmosphere feels a bit different. I am sure having a baby around a working environment changes the tone a little bit.”

Ardern is enjoying the change, she says. Even being woken up at night by Neve has elements of joy. “It sounds probably contradictory but that is how we’ve felt.”

Facebook Twitter Pinterest Baby seat in the office of Jacinda Ardern.

The media is also on a learning curve. On Friday the state broadcaster Television New Zealand apologised after posting footage of Ardern breastfeeding in public online.

Neve’s nursery is a combination of a boardroom and a kitchenette inside Wellington’s parliament building, which is known as the Beehive. Here, Ardern has squeezed a changing table, bassinet, a desk for her partner, Clarke Gayford, and “blankets, booties and hats” sent as gifts after the birth.

“Basically it is a small kitchenette where usually I would make a cup of tea, but it’s got just enough space for her to be there,” Ardern says.

The plan is that Neve will mainly be looked after by Gayford, but in these early weeks and months will be with Ardern as much as possible. The prime minister is determined to make it work for her daughter, and the country.

“There’s every chance if I was in a different set of circumstances I would have done that transition [back to work] differently or had a bit more time. But I have the privilege of doing this job and I have to say the privilege of being a mother too. So I am making the combination I have work for us.”

I have the privilege of doing this job and I have to say the privilege of being a mother too. So I am making the combination I have work for us Jacinda Ardern

New mothers in New Zealand are eligible for 22 weeks’ paid maternity leave, to be increased to 26 by 2020, but Ardern chose to take just six weeks in a move that divided opinion. In her absence, the deputy prime minister, Winston Peters, held the reins, causing a couple of minor controversies.

“I never felt comfortable with the idea [of having more time off],” says Ardern. “Having been elected to be prime minister, to be away from the job for that length of time … I absolutely believe in 26 weeks, I absolutely do. But I have to acknowledge that this role is a very privileged one and it just personally didn’t feel right to me to be away for any longer than I was.”

“In my mind this job is 24/7, and it definitely didn’t stop over the six weeks. There were moments where I would think: OK, when I go back to work, how am I going to make this particular thing work? It gave me the time to just think that through a little bit and talk it through with Clarke. So I was constantly thinking about that side of things.”

Facebook Twitter Pinterest Jacinda Ardern with her partner, Clarke Gayford, and baby Neve at Wellington airport. Photograph: Hannah Peters/Getty Images

Ardern’s time away from work in her Auckland home – where she was left alone by the media, the public and most of her staff – gave her space to reflect on some of her government’s keystone policies. Her commitment to ending child poverty in New Zealand has predictably been strengthened, but so too have other ambitions.

“What I probably came away with was a better understanding of the way our midwifery system works, the way our Plunket system [free healthcare for under-fives] works, even postnatal care. I have already been a big believer in a model of nurse/family partnerships. The idea of having – for those mums that might benefit from a bit of extra support – having those visits scaled up a bit. I believed in it before; I absolutely believe in it now. So that is probably one of the things that affirmed something I already supported.”

Next month Ardern, Gayford and Neve will travel to New York for a United Nations general assembly. Discussing climate change and the rights and wellbeing of women and children worldwide will be among Ardern’s priorities. After Donald Trump’s recent trade threats, stabilising and strengthening international trade agreements will also be on the agenda.

“There’s probably a tendency to view power … to be either based on size or the size and power of your economy. I think New Zealand’s strength has always been using our voice on the issues that matter and we’ve been consistent on it. There is power in that,” says Ardern.

“Right now, I think that voice has to speak in favour of the power of the collective and the importance of the international community. We can’t act like individual agents that have no effect on one another. The position we take on trade and the environment and climate change affects one another in this globalised world. So we need to use our power for good.”