"It's been incredible actually, I've been told that only 2 per cent of people actually deliver on their due date," said Ena Lu, a commercial analyst.
"Everyone in my family is like 'wow', surprised and excited as well. It's the first grandchild for my husband's side of the family, so we're all pretty excited."
Lu, originally from Hong Kong, said her Taiwanese father-in-law had just arrived in New Zealand and would be deciding the baby's Chinese name.
"The name needs be based on when they are born, and that will determine what [Chinese] characters are used in the name," she said.
She said it was a long labour, having arrived at hospital at 7.30pm on New Year's Eve, but looked to be in good health and spirits after welcoming her first born.
Meanwhile, 18-year-old Kimberley Thomas ditched the usual New Year's Eve parties for the maternity ward to deliver the country's first baby girl.
Baby Kya Thomas-van Luit, weighing 3.3kg, was born at 12.15am at west Auckland's Waitakere Hospital.
"My due date was the 31st, but this still came as a huge surprise," Thomas said.
"I was having really strong contractions and then as soon as I hopped out of the car, my waters broke. I had to come inside and was pushed in straight away, it was so quick."
Thomas said it was an "interesting way" to spend New Year's, and one that she'll never forget.
"Everyone else is out partying, and here I am having a baby," she said.
"But I guess it's really special to have a new year baby, and something that family and friends will certainly talk about."
Grandmother Rachel Krum said she was on holiday in Taupo, and rushed back when she got the news.
"It really came as a surprise...but it's exciting times for all of us," Krum said.