Time magazine reports that Ardern, flew out to NY with her partner, Clarke Gayford and Neve, delivering a speech on Monday night at the Nelson Mandela Peace Summit, with Neve nestled in the front row. "Great yarn for her 21st (birthday)", he joked on Twitter.
But her daughter Neve also stole the limelight - sitting in the General Assembly with her own, specially made UN ID.
She said apologised to passengers ahead of their flight to NY as the pair took baby Neve on board.
While the leader delivered her speech, Ardern's partner Clarke Gayford held the infant on his lap.
At just three months, she is said to be the youngest person to ever attend the United Nations General Assembly in NY. Ardern said she discovered the pregnancy within a week of her election victory previous year.
The PM told the New Zealand Herald she would bear the cost of her partner's travel, as "he's primarily travelling to care for Neve".
She is her country's youngest premier and the first to take maternity leave while in office.
Earlier on Monday, she spoke at the launch of the annual "Climate Week" event. "She's a good sleeper and we don't know whether that will mean she ends up sleeping a lot in the day rather than the night". She is also only the second elected world leader to give birth during her tenure, after Pakistan's Benazir Bhutto in 1990.
"I have the ability to take my child to work, there's not many places you can do that. I am not the gold standard for bringing up a child in this current environment because there are things about my circumstances that are not the same".
Her work-life balance was again questioned last month when breastfeeding baby Neve necessitated an extra flight in order for Ardern to both attend to her newborn's needs and appear at the Pacific Islands Forum in Nauru.
"If I can do one thing, and that is change the way we think about these things, then I will pleased we have achieved something".
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