Ms Ardern yesterday took up the reins of leadership again, six weeks after handing over the country to Deputy Prime Minister Winston Peters, as she took maternity leave.
Ardern, 38, is just the second elected world leader in recent history to give birth while holding office.
While the young gun politician officially returned to work on Wednesday at midnight, Ardern admitted she hasn't been completely off-duty and received regular visits from staff with "suitcases" of government papers for her.
Ms Ardern will fly to Wellington on Saturday to set up in the Prime Minister's residence near the Beehive, with her partner, Clarke Gayford, and their daughter Neve. But she added that she's keen to get back to work.
"Ultimately though, that first week back, I am going to be focused on getting straight back into it".
Top questions for the new mom is how she'd be able to handle motherhood and her role as head of state.
"I'm not the first woman to work and have a baby", Ardern has said. When she announced her pregnancy, shortly after becoming prime minister past year, she said she would take six weeks of maternity leave.
Ardern became only the second leader of a country to have a baby while in office when she gave birth to her daughter Neve on 21 June. On a personal level, just from day to day - I'm a mum and need to meet all the responsibilities that come with being a mum.
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"As parents, one of the first things we have to learn is juggling many different roles and Jacinda Ardern has been multi-tasking like every single parent I've ever met over the past five weeks on maternity leave".
"All I can do, really, is give people reassurance that it won't [affect the job]", she said at the time "But I know I'm going to have to prove it".
"Neve didn't choose my political life", she said.
Ardern said in media interviews that Neve would travel with her for the timebeing given she is breastfeeding and would accompany her on a trip to NY for the U.N. General Assembly meeting in September.
In a television interview, Ardern said, like other parents, she has been "so focused on food, nappies and sleep".
"But, of course, that needs to be fulfilled by further demonstration that there will be denuclearization", she said. "I thank the US Congress and President Trump for their support of the Act".
"I also have the ability to have [Neve] with me [at work] so that means that I'm privileged and I'm lucky, a lot of women don't have that choice".