Rotorua mums Jacinda Higgins (left) and Leonie Neilson with their heart babies Emma Barber, 11-months, and Jesse Neilson, 2.
Before Jacinda Higgins became a mum, the only type of heart she knew about was the kind you get on Valentine's Day.
Now she can draw an anatomical diagram of what a normal heart should look like.
Why? Because her daughter Emma does not have a normal heart.
At 34 weeks pregnant, Ms Higgins was told her baby had pulmonary atresia, a hypoplastic right ventricle, atrial septal defect and hypoplastic tricuspid valve.
"We were completely heartbroken. Emma's my first baby and I had no idea about heart conditions or how common they were. The news came as a total shock."
Emma had her first open heart surgery at just 4 days old. Her second was at 5 months old.
"My partner and I have had such a supportive family and charities like Heart Kids and Ronald McDonald House have been there since day one but it is hard, you're always worried."
But despite her challenging start, the 11-month-old is a "giggler" who shows no sign of wanting to take life slowly.
"There will be more surgeries but we just have to play it by ear. She will have her limitations - she doesn't get over colds or infections as well - but she will be able to lead a pretty normal life."
It is for Emma and others like her that Ms Higgins will be plunging into icy cold water today as part of the Heart Stopper Challenge.
Rotorua mums Jacinda Higgins (left) and Leonie Neilson with their heart babies Emma Barber, 11-months, and Jesse Neilson, 2. PHOTO/STEPHEN PARKER
Held at the Rotorua Aquatic Centre, the challenge requires people to submerge their body in icy-cold water.
The challenge mimics what it is like for a child to have ice water flushed through their chest cavity for certain times of open heart surgery.
"I love getting involved in charity events and this is a way to give back to a charity that has given so much to us.
"It's also about experiencing a tiny bit of Emma's reality. I'm always wondering what she feels, what she remembers. I will go through a small discomfort to get a glimpse of that."
The annual event is organised by Heart Kids Rotorua, a non-profit organisation dedicated to supporting Heart Kids and their families through their journey.
Committee member Leonie Neilson will also be taking the plunge.
She was told at 20 weeks pregnant her baby had coarctation of the aorta - a narrowing of the major artery.
Mrs Neilson said it was hard to be sat down in a room and told there was a problem with her daughter Jesse, now 2.
"It was horrible to hear. Our' is not as hard a journey compared to others but you're always a little bit on edge, your 'normal' becomes different.
"She's had one open heart surgery but it didn't go as well as expected so there will have to be another one.
"I'm doing the plunge to support Heart Kids and help raise awareness of what these little guys have to go through."
Every week, 12 babies in New Zealand are born with a heart defect. More than half of these conditions are serious enough to require treatment or surgery.
What: Heart Stopper Challenge Where: Rotorua Aquatic Centre When: 12pm to 4pm Why: To raise awareness of heart defects Donate: http://heartstopper.org.nz/event/hscrotorua17
