Unlike Ardern's other interviews in the US, baby Neve's only appearance was in the introduction and a photo at the start, at which the audience went "aaahhh".
After that Ardern was left to rely on pure nerve and wit rather than a cute baby.
She did this with some aplomb, especially given it was the end of a long day in New York.
Ardern must surely also have been a tad nervous - The Late Show with Stephen Colbert is watched by four million people and was the most risky of the interviews she has done in the US. It was a minefield of potential diplomatic blunders.
Sure enough, it was not long until Colbert raised Trump.
He asked about the world leaders at the UN laughing after a boast by Trump and wanted to know if Trump was right to say they were laughing with him rather than at him.
As Ardern's troupe of officials sitting at the very top of the Ed Sullivan Theatre hoped and prayed, the diplomat in Ardern wrestled with the wish not to be a damp squib.
She informed him the leaders were laughing with Trump upon a second laugh, but remained mum on the status of the first laugh. That was "a spontaneous murmur".
Then came a question about Trump's notorious handshakes.
"I went in for a natural shake. I have a quite firm handshake, and I didn't particularly notice," Ardern said.
Colbert said he had noted her firm handshake himself to which she replied "it's the way we shake in New Zealand."
That prompted Colbert to observe New Zealanders were "a very vital people - very vigorous."
"I don't think I've ever heard us described in that manner," Ardern said. "Vital. It makes us sound like a health product."
It got her a laugh, and if you're making people laugh in the USA you're winning.
But Ardern's primary mission was to get in a sales job for New Zealand.
Colbert is renowned as a Lord of the Rings fan and Ardern came bearing precious gifts from one of the towns she grew up in - Matamata, where Hobbiton is based.
She offered Colbert citizenship of Hobbiton. "You get a mug," she said, and as he questioned "where's the paperwork", she added in a certificate with calligraphy.
"Come to New Zealand and we'll make the ceremony official. There's a direct flight from Chicago from November, so it's nice and easy."
Plug for New Zealand in the USA? Tick. Plug for Air NZ. Tick.
The Late Show is recorded a few hours before it screens. When Colbert stuffed up a gag, he said to the audience: "we'll fix that in post [production]. And no one will know I'm a f*** up unless one of you tweets."
How handy it would be for a Prime Minister to simply pre-record every decision and word and fix it in "post". Those signs saying "applause" at the relevant moment might do well too.
But on the night, Ardern needed neither. On Friday morning Ardern will follow in Trump's footsteps and deliver her own statement to the UN General Assembly.
Colbert wished her luck. Then he added: ''I hope everyone laughs."
