Ian works in property for the Salvation Army and Raewyn is a "stay-at-home-mum", and in the past looked after up to three babies at a time.
They arrive at short notice at Ian and Raewyn McLaren's home.
Newborn babies, sometimes just a few hours old, fragile, compromised and in desperate need of care and love.
The defenceless infants are some of New Zealand's most vulnerable babies.
Under the McLarens' care the babies thrive. They are loved and cherished and given the best possible start to life.
Ian and Raewyn are foster parents. What began as an interest 15 years ago has become a way of life for the couple, who are now caring for their 100th baby.
"I've got a passion for babies," Raewyn said. "I love doing it."
Babies are brought to the couple from Child, Youth and Family. They have been taken from the biological parents under care and protection orders amid concerns of addiction and child abuse.
Others come from teenage mothers considering giving the baby up for adoption. While she decides, the foster parents step in.
The McLarens raised four children of their own and when their youngest son was 18 the couple took in their first babies: twin boys.
"They were the hardest," Ian said. "After three months we stood waved goodbye and felt empty."
Saying goodbye was so difficult Raewyn thought she couldn't care for any more babies but it became easier.
"It's fine now, I'm well used to it," she said. "At the beginning I couldn't part with any of them. I wanted to keep the whole bang lot. But now I just hope they are going to get as much love and care as I've been able to give them."
Ian works in property for the Salvation Army and Raewyn is a "stay-at-home-mum", and in the past looked after up to three babies at a time.
For many babies, the couple are weaning them from drug addictions developed in the womb.
But Raewyn says she doesn't see it as hard work. "I'm quite happy to get up during the night, do the feeding, get them in a routine. I'm probably an old-fashioned mother."
The longest they have cared for a baby is eight months, but usually the babies go to a new home at at 2-6 months old.
Babies are usually rehomed with whanau, through Home for Life, or placed into New Zealand's adoption pool. Occasionally a mother decides to keep her baby.
In 2013 the couple were humbled by Queen's Service Medals for their work.
But more rewarding are the simple milestones such as a smile or interaction.
"If you give them that good start and if they bond with you and then there's a good transition they will bond well with whoever is the long-term carer."
About 12 years ago the couple considered adopting a baby girl they were fostering but age was against them. Occasionally they see some of the children they have cared for over the years and for one of Raewyn's birthdays Ian invited a bunch of the fostered children and their families as a surprise for his wife.
The nursery at the couple's home is fully stocked with all the furniture and equipment needed, including a wardrobe full of baby boys' and girls' clothes.
An allowance for the work does not stretch far.
"By the time you buy disposable naps and formula, there's not a great amount left," Raewyn said. "But I'm not doing it for that. You've got to have a lot of love and patience and cherish them.
Raewyn said the only difference between mothering now and back in the 1970s is that she uses disposable nappies.
For now there's no end in sight. Sometimes Raewyn thinks she has "had enough" but every time they get a call to care for a baby, she just can't say no.
Each day on The Great New Zealand Road Trip, we catch up with a noteworthy Kiwi.