Maddy Rybkin, now two, was born with a condition called Polycystic Kidney Disease (PKD), which meant cysts grew on her kidneys causing her stomach to look enlarged.
Although Maddy's condition was managed early on, when she reached 18 months old her parents, Paul Rybkin, 38, and Karen Rodas, 38, were told she urgently needed a kidney transplant.
Luckily, her dad was identified as a donor and, following a life-saving operation in January 2016, she has recovered well.
"Any father would have done what I did, donating my kidney to Maddy," Rybkin said. "It’s part of being a parent.
"Now we are on a high and can watch Maddy grow up as a happy and healthy little girl.”
Maddy’s parents, from New Jersey in the US, are both carriers of the recessive gene for PKD - a genetic condition that leads to the deterioration of kidney and liver function.
The couple found out they carried the recessive gene when Rodas, who is also mum to Jackson, nine, from a previous relationship, and one-year-old Penelope with Rybkin, - fell pregnant with their first child together, Nathaniel.
Rodas carried Nathaniel until full-term, but he died after just 36 hours.
“During my pregnancy with Nathaniel, we discovered we both carried the recessive gene PKD, meaning the chances of any of our babies surviving, if they were born with it, was very low,” Rodas said.
“He didn’t stand a chance. Just 36 hours after his first cry brought him to life on 4 August 2012, he was gone.”
Medics warned the couple if they tried for another baby, he or she would have a 25% chance of carrying the condition, too.
But Rodas and Rybkin didn't want to let go of their dream of having a big family.
“When I fell pregnant again, we were both over the moon,” Rodas explained.
“Then, at our 20-week scan, doctors found Maddy’s kidneys were enlarged - a sure-sign of PKD, just like Nathaniel. My heart sank.
“I was determined we didn’t lose our baby to the deadly disease again.”
The family found a doctor in Philadelphia who knew how to look after babies with PKD.
In November 2013, they travelled to the Children's Hospital of Philadelphia for what should have been a routine scan at 33 weeks.
However, Rodas had to be induced to bring on labour early, to save Maddy as she had become entangled in the umbilical chord.
After 12 hours, Maddy arrived. Her stomach was bloated, which doctors said was a symptom of her condition.
Maddy was kept in hospital for seven weeks, and on Christmas Eve her parents surprised their family by bringing her home.
For the next year and a half, Maddy was a happy little girl who, despite still needing tubes and oxygen at home and regular hospital visits, was doing well.
But then her kidneys started to fail and a transplant was needed urgently.
After Rybkin was identified as a match, the operations took place on 19 January 2016.
“With Paul and Maddy, two of my most precious souls, going under the knife, my nerves were a wreck,” Rodas said.
“I kept thinking ‘What if something happens to them both? How will I cope?’”
Thankfully, both operations were a success.
And, after a few weeks of rest, Rodas said Maddy seemed like a completely different child.
Rodas continued: “Daddy's kidney has saved our little girl.
"She has boundless energy. Her massive tummy now just looks a little bit rounded and she is a happy and healthy two-year-old.
“She will need another transplant in 25 years, but that feels like a lifetime away.”
To follow Maddy’s journey, visit www.facebook.com/aKidneyForMadeline.