Lucy Robinson, 30, and her husband Tim, 42, knew they could never be parents naturally after Tim's battle with testicular cancer at the age of 27.
The couple had fertility treatment using donor sperm, but Dr. George Nwadke from CARE Fertility in Nottingham discovered there was another problem stopping Lucy getting pregnant. Her own body was producing cells that were killing her fertilised eggs before they could develop.
He suggested an unusual approach to lower her immune system - injecting her with protein taken from a chicken egg!
Lucy was given an intralipid solution containing a combination of egg extracts and soy oil through a drip, before being inseminated with the fertilised eggs.
Research shows the fatty acids in the egg reduce the number of killer cells in the immune system.
Finally in January last year, Lucy discovered she was pregnant, and gave birth to baby Theo, weighing a healthy 8lb, 11oz, in August.
Lucy, a nanny, says: "When I held Theo in my arms it was the most amazing moment. We just couldn't believe that we were parents at last.
It had seemed like an impossible dream - yet it was all made possible because of the yolk from a hen's egg. It really is remarkable.
Tim, a train driver, first suffered from a torsion of the testicle when he was just 17, where the spermatic cord to a testicle twists, cutting off the blood supply. He had to have an emergency operation to remove his testicle.
He then suffered further problems 10 years later when doctors discovered he had testicular cancer.
"I noticed my remaining testicle was swollen and I went to see the GP who referred me to hospital. I was hoping that it wasn't anything serious, but the possibility of testicular cancer was in the back of my mind," explains Tim.
The tests showed not only that he had testicular cancer, but that it had spread to his lungs and back too. He underwent chemotherapy treatment and an operation to remove his remaining testicle which was successful - although it left him unable to have children.
"It was upsetting being told that I wouldn't be a father, but I was just concentrating on beating the cancer at the time. It was worrying that it had spread and I just had to pray that the treatment would work. Luckily it did and I managed to pull through."
The couple, who live in Bridgewater, Somerset, underwent their first course of fertility treatment in January 2007, where they tried artificial insemination using donor sperm.
That failed, so they underwent another two courses of artificial insemination, but those failed too.
"It was devastating when all the treatments failed," says Lucy. "We had pinned all our hopes on it working, as we had been able to use donor sperm. We never thought that it would be a problem for me to fall pregnant."
Next the couple underwent three courses of IVF treatment - but they failed each time too.
"It was just an emotional rollercoaster. Each time we had the treatment, we would get our hopes up that this time we would actually be parents," says Lucy.
But each time it failed. I produced good quality eggs, which would then be fertilised, but I would fail to fall pregnant. It was difficult to keep going after each failure, but we were so desperate to be parents.
Then the couple went to CARE fertility in Nottingham where Dr. Nwadke discovered that Lucy was producing cells that were attacking the embryos when they were implanted back into her womb.
"It was a relief when the doctors discovered what was wrong. I couldn't believe that my own body was attacking the embryos. I had never even heard of it happening before."
Lucy underwent her fourth course of IVF treatment at the end of December 2010, and she was injected with the egg yolk mixture. She finally discovered she was pregnant two weeks later. Her pregnancy went smoothly and she gave birth to son Theo at Musgrove Hospital in Taunton.
"It was so amazing to finally be pregnant after all these years of trying. We were overjoyed. We couldn't believe that we were actually parents at last, after everything that Tim has been through and all the treatment that we've had.
Finally we have our miracle son - and its all thanks to a hen's egg yolk. It really is remarkable.
Simon Thornton, Group Medical Director, CARE Fertility, said: "We believe that this treatment is important for women and families because there seems to be a subset of fertility patients who have developed, effectively, over-active immune systems and this is contributing to their fertility difficulties. We have devoted time to finding answers when nature goes wrong."
What a remarkable story. Congratulations Lucy and Tim!