Doctors suggested that her mum Kerry Healey, 39, a supermarket worker from Gloucester, had a termination when they discovered all the defects when she was pregnant with her daughter.
But the brave mum refused as she wanted to give her tiny daughter a chance at life, despite doctors not knowing if she would survive when she entered the world.
Now after several operations, brave Millie has defied all the odds.
Her proud dad Graeme, 41, a house husband, says: "We cannot believe that after everything Millie has been through, that she is still here with us. But she has just celebrated her first birthday and she's doing so well. We refused to give up on her and she has proved everyone wrong."
The problems were discovered when Kerry was 20 weeks pregnant. The first problem that showed on the scan was that Millie had hyperplastic right heart syndrome, which meant that she only had half a working heart.
"We were absolutely shocked. We had never even heard of this condition before," explains Kerry. "Our baby had just half a working heart, and we didn't know if she would survive."
Six other life-threatening heart conditions were then identified, and the doctors suggested that the couple consider a termination.
"They likened her heart to something that had been built without a construction manual and by a person who was blindfolded. There was just no structure to it at all," says Graeme.
On a scale of one to ten, with ten being the most serious, they rated her heart as a 14. They gave her no hope of survival. But we were refused to have a termination. We wanted to let nature take its course. We had to give our little girl a chance, we couldn't take that away from her.
Kerry was given regular scans throughout the rest of the pregnancy, and each showed that Millie was still alive. She was born last May at St Michael's Hospital in Bristol, weighing 4Ib, 15oz, but as soon as she was born her heart stopped and doctors had to rescucitate her.
Kerry says: "It was an emotional rollercoaster. She had survived the birth, but then doctors had to bring her back to life. They spent all weekend trying to stabilise her condition and they told us they didn't think she was going to survive.
"But she hung on, and refused to give up. She was such a little fighter."
Millie was then taken for a CT scan of her heart. The seven defects were so severe that doctors told her devastated parents that the kindest thing would be to let her die.
"The defects were all so complicated that the doctors thought the best thing would be to give her palliative care until she passed away," says Graeme. "But we refused. She had come through so far, we weren't going to give up on her now."
"It was a complicated operation because she was so small, but she survived it. It was such a relief when she came out of the operating theatre and it had been a success," says Graeme.
Millie has had a further two operations, to further re-plumb her heart. She will need a third procedure in a few years time, but at the moment the circulation in her left lung is so restricted that the operation isn't possible.
The couple, who have seven other children between them, are hopeful that surgeons will find some way of helping her. Another possible course of action will be for her to undergo a heart and lung transplant.
"We just have to take each day as it comes with Millie. She has done so well so far, but her case is so complicated that we don't know what the future holds," says Graeme.
"Millie's seven heart defects:"
1. Transposition of the great arteries
2. Anomalies of the pulmonary venus drainage
3. Double inlet and outlet of the left ventricle
4. Hyperplastic aortic arch
5. Hyperplastic right ventricle
6. Tricuspid valve atresia
7. Total pulmonary stenoisis of the left lung
Words: Lucy Laing at Worldwide Features
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