Primary school teacher Gill Bay and mental health support worker husband Keith were meant to be hosting the celebration of their first child's impending arrival, but little Nathanael Mark crashed the party.
The 1.5kg (3lb 4oz) boy, who arrived more than a month early, is "small but healthy … and absolutely beautiful", his mum told The New Zealand Herald.
"I feel so emotional and just thanking God for everything. I never thought this pregnancy can happen, because of all my fertility issues before … we waited four years to conceive.
"We've been praying and hoping this time will come, and this is it - we are parents."
The Papakura couple had just got into their car after leaving West Auckland megastore Costco Westgate when Bay realised she could not stay seated, and felt like she wanted to go to the toilet, a continuation of feelings and discomfort she had been experiencing overnight.
Her midwife had earlier told her she was probably suffering from constipation, prescribing laxatives, so the mum-to-be returned to the store to use the women's bathroom.
But it was not long before a Costco worker, and fellow Philippines native, came to check on her.
"I started crying because of the pain, it's getting stronger and stronger … so someone heard me and she said, 'Miss, are you okay? Are you pregnant?'
"I was so desperate for help that I opened my cubicle door and said, 'Yes, please help'."
The worker and another woman - a mother herself - eventually helped the 31-year-old move to the disabled toilet, where soon after she realised that she was giving birth.
Her husband, who had joined her in the toilet, then saw the baby was crowning, Bay said.
"I immediately moved [onto] my hands and knees … I was trying to use what I learned from watching YouTube.
"And thank God the toilet was so clean and not disgusting, and everything's just perfect, and there's a chair that I can hold onto if I need to."
At 3.04pm, and after a single push, baby Nathanael was delivered into his father's arms at 35 weeks and five days gestation.
"My husband, he was the one who caught the baby, he was like the midwife there. And the baby came out in a sac with the placenta. Everything came out together … it was beautiful."
To add to an already unusual situation, Nathanael's birth was a rare case of en caul - a term used to described the birth of a foetus and placenta entirely encased in an unruptured amniotic sac.
En caul births occur in fewer than one in 80,000 vaginal deliveries, according to the US Government's National Library of Medicine.
However, the situation initially frightened the new parents, because they did not hear the newborn cries they expected, Bay said.
"My husband started to say, 'Oh, come on baby, I want you to cry', and I was crying and praying to God, I hope the baby is okay."
After a female Costco staff member was found who was comfortable pinching open the sac, Nathanael let out a hearty cry.
"That's the relief, when I heard him cry and they said that everything's okay."
"They were clapping and saying congratulations. I was just so thankful that everything went well and the baby is alive and healthy, I was crying and thanking God for that and that people are helping us - people we don't know - and they were so compassionate and kind.
"To the Costco staff and everyone involved, paramedics and Waitākere Maternity, your kindness and fantastic support has deeply touched us. The safe arrival of our precious baby would not have been possible without your assistance, and for this, our gratitude knows no bounds ... thank you."
Costco did not want to comment when contacted by the Herald, but the megastore has been in touch with Bay's sister-in-law, although the new mum's yet to hear details, she said.
The Eden Christian Academy School teacher had also read comments about the birth on the Costco NZ Westgate Community Facebook page, where well-wishers had suggested names including Costco's home brand Kirkland, Coco and Aisle.
While the couple had chosen Nathanael - which means gift from God - she expected her little boy would inevitably have a nickname nod to the place he came into the world.
"I think he's gonna be known as Costco Baby."
A day on she still found herself struggling to believe she had given birth in Costco - an experience believed to be only shared by one other mum, a British woman who delivered a son in the tyre section of a London Costco in 2017.
"It's like in the movies, things like this. I didn't expect it's going to happen to me."
