The tricuspid valve lies between the two chambers on the right side of the heart.
The valve opens when blood flows from the right atrium to the right ventricle.
At 37 weeks pregnant, Ally moved into Starship Hospital while Mike continued to work back home in Te Awamutu at JVR Automotive.
Their first daughter, two-year-old Holly, spent her weeks between Auckland with mum and Cambridge with her Oma (grandmother), Petra Pullenger.
Naia was born on March 20 at Auckland Hospital and went straight into the neonatal intensive care unit, with a heart procedure scheduled for the next day.
The family spent a month at home before returning to Auckland for Naia's first open heart surgery, which she took 10 weeks to recover from.
In her first surgery, doctors joined the pulmonary artery — the artery carrying blood from the right ventricle to the lungs — to the aorta using a 4mm silicone shunt.
This allowed blood flow from the left ventricle to the aorta.
"In simple terms, doctors 're-plumbed' her heart," Ally says.
During this time Ally and Naia spent their days in Starship, with Naia needing to be checked every four hours and fed through a tube.
Meanwhile, in Te Awamutu, Mike was working full-time, driving to Auckland on Friday after work, and returning to Te Awamutu at midnight on Sunday.
The weeks were lonely and the young family was struggling being apart.
However, in July, Mike decided to leave his job — a choice he says was scary and risky.
Mike then moved up to Auckland's Ronald McDonald House with two-year-old Holly.
Mike and Holly spent their days visiting Ally and Naia at Starship, a 10-minute walk away.
They have fond memories of Ronald McDonald House.
They are grateful for the shared meals with other families staying there and enjoyed the vouchers for the zoo or museum.
Despite the hard times, there have been a few unexpected pleasant surprises.
For Mike, a silver lining was spending quality time with his two year old.
Mike and Ally also enjoyed getting to know family members living in Auckland.
They say they have felt a sense of peace in the situation, crediting their Christian faith and support from North End Church in Te Awamutu.
Naia had her second surgery in August.
The silicone shunt was removed, allowing deoxygenated blood to flow directly to the pulmonary arteries, reducing ventricular workload.
She will have her third and final open heart surgery at age three or four.
One of the hardest things for Ally was having her role of mothering taken away and putting her baby in the hands of doctors and nurses.
However, she found it was easy to trust the professionals and the couple are optimistic.
Mike and Ally have had a whirlwind three years since they were married in 2015.
They met at Finlay Park Adventure Camp on the shores of Lake Karāpiro as teenagers.
Ally, who attended Cambridge High School, was a youth leader at a children's camp and Mike worked as an outdoor instructor at the camp.
In the last three years they've married, bought and renovated a house and had two children.
Last week Mike completed his apprenticeship and is now a qualified automotive technician.
It's a lot to take on for Ally, 22, and Mike, 23, but they wouldn't have it any other way.
"It's all a part of our story," Mike says.
"When we found out Naia would have a heart condition, we were just so thankful to know that she had a chance of surviving."
This Friday Mike and Ally are leaving Te Awamutu to start a new chapter in Whāngarei, where they have bought a house and secured a job for Mike.
It will be a bittersweet farewell when they leave Te Awamutu — a community that has rallied around them.
Throughout the last year they've received support from friends, family, members of their church and strangers.
"People have made meals for us, donated money, mowed our lawns and prayed for us — and those are just the offers of help we accepted."
