And it's all thanks to his parents' determination to fight for him while he was still in the womb.
Doctors warned Lucy Hay, 37, and her partner Stuart, 41, to expect the worst in April 2011 when they discovered their unborn baby was suffering from Congenital Diaphragmatic Hernia (CDH) - a hole in the diaphragm which allows organs elsewhere in the body to move into the chest cavity which prevents the lungs from forming correctly.
In desperation Lucy and Stuart scoured the internet for new treatments and discovered a pioneering procedure that could give Thomas a chance.
The operation, which is carried out in the womb, is called Fetoscopic Tracheal Occlusion (FETO), which involves inserting a tiny balloon into the baby's trachea using keyhole surgery.
Once inflated fluid builds up in the baby's lungs forcing them to grow.
Thomas had the operation at King's College Hospital in London and thanks to the balloon his lungs increased in size dramatically. Now Thomas has amazed doctors by making a full recovery.
Recalling the moment she found out there was something wrong with her unborn child, Lucy, who lives at St David's College in Llandudno, told her local newspaper: "I knew there was something wrong as the sonographer was unusually quiet and had a serious look on her face.
"Then came the words that will haunt me for the rest of my life, 'What I am seeing is not quite what I should be seeing'."
She added: "We arranged to go to King's College Hospital in London, where we were very bluntly told Thomas would almost definitely die at birth as his lungs were a tenth of the size they should have been.
We had three options. Firstly, a termination; secondly, carry on with the pregnancy, give birth and then plan a funeral; or finally, take part in a medical trial involving keyhole surgery which would increase his chances of survival to 50 per cent. It was as honest and as blunt as that.
"I never considered terminating the pregnancy. However low Thomas's chance of survival was, we couldn't take it away from him," she said.
Two weeks later Lucy was admitted to Liverpool Women's Hospital when her waters broke as a result of the operation. She feared the worst and thought it was all over for her unborn son.
But her pregnancy continued for another 11 weeks and at 37 weeks pregnant, Lucy was induced.
Thomas had his hernia repaired when he was two days old at Alder Hey Children's Hospital. But a week later it was discovered he had a condition that caused his windpipe to collapse as he breathed out, which was a consequence of the operation. Thomas had to go to Great Ormond Street for a procedure to help strengthen his windpipe.
After three months in hospital Thomas made it home for the first time last October.
"We couldn't believe it when we finally got him home, I'd never imagined the day would ever come," said Lucy.
Thomas has been in and out of hospital since then, but he is a determined little fighter and each time has recovered quicker as he was older and stronger.
"It has been a long, hard, emotional and completely traumatic journey," said Lucy.
"After the first scan I convinced myself I was going to lose my baby. I did not allow myself to look to the future as it hurt so much.
"I know for sure that miracles do happen and I believe Thomas is one of them."
What an uplifting story!
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