One of Britain's youngest surviving heart transplant patients has celebrated her 18th birthday. Kaylee Davidson was just five months old and expected to die within days when she underwent surgery in 1987.

One of Britain's youngest surviving heart transplant patients has celebrated her 18th birthday. Kaylee Davidson was just five months old and expected to die within days when she underwent surgery in 1987.

The donor heart was the size of a plum and doctors were not even sure that it would grow with her but she is now a healthy adult who campaigns to increase the number of people on the organ donor register.

As she celebrated her birthday at a fundraising lunch for transplant charities, Ms Davidson said: "I grew up with the feeling that I was special and I do feel lucky to be alive.

She added: "I often think about my donor family and can't thank them enough for the second chance I was given to live. I am living proof that people can make a difference by becoming an organ donor."

The teenager takes four tablets a day to prevent rejection and control her blood pressure, but otherwise leads a normal, healthy life. She is studying performing arts and dance at college in Sunderland and is due to represent Great Britain in the World Transplant Games in Canada this summer.

She first took part in the Games when she was just two years old, competing in a wellie-throwing competition.

Ms Davidson was born healthy but within a few weeks, developed cardiomyopathy, a virus that destroys the heart muscle.

She was taken to the Freeman Hospital near her home in Newcastle upon Tyne and placed on the waiting list for a donor heart, but doctors warned her parents that nobody in Britain had attempted a transplant on such a tiny baby before.

Surgeons in the United States had operated on babies her age, but the infant patient was too ill to be flown abroad for treatment.

Lynne Holt was the transplant co-ordinator dealing with the Davidson family when a heart was found for their daughter. She sat with Mr and Mrs Davidson throughout the five-hour operation and has remained close friends with Ms Davidson.

Ms Holt said: "The call came in one late afternoon when Kaylee had been on the transplant list for about three weeks.

"She was critically ill in intensive care and we were amazed that a heart small enough had been found. When we were doing the operation we couldn't believe how small the heart actually was - it was the size of a plum.

"It was incredible because nobody had operated on a baby this small and we didn't even know whether the heart would grow with her or not."

The donated heart came from a baby girl of around Ms Davidson's age who had died in a car crash, along with her mother. The dead baby's father was in the crash but not injured and had to make the decision to donate her heart.

Ms Holt said: "It must have been an incredibly hard thing for him to do but it saved Kaylee's life. He knew the heart had gone to her but they have never met.

"This case just shows why people should talk about organ donation and go on the register."

Chris McGregor, the surgeon who operated on Ms Davidson, now works in the United States, although Ms Holt is still working at the Freeman Hospital in Newcastle. Mrs Davidson said: "It only seems like yesterday that all that happened. The doctors performed what at the time seemed like a miracle.

"To get her back and see her flourish into the lovely, healthy teenager she has become has been amazing."

She added: "It can happen to anyone - we were an ordinary family who had something extraordinary happen to us."

Only one other child in Britain has undergone a transplant at a younger age and is still alive - a boy who was operated on at seven weeks in 1997.

Little miracles

* Louise Brown was the world's first baby to be born after in vitro fertilisation (IVF). Born on 25 July 1978 at Oldham general hospital in Greater Manchester, her arrival marked a revolution in fertility treatment. Within six months, more than 5,000 people in Britain had applied for IVF treatment and since then more than a million "test-tube babies" have been born.

* Britain's smallest surviving baby is Aaliyah Hart, who was born weighing 12 ounces in May 2003. She was 12 weeks premature and had failed to grow in the womb, meaning she was just 9 inches long at birth. Doctors gave her a 10 per chance of survival, but she defied the odds and is described by her mother as "bright as a button".

* In 2002, Rhys Evans was the first child in the UK to undergo gene therapy to cure a potentially fatal condition that had left him with no immunity to infection. Until he was 18 months old, Rhys had spent most of his life in hospital with severe combined immunodeficiency (SCID), also known as "baby in a bubble" syndrome. Doctors took bone marrow from Rhys and used a virus to correct the faulty gene and boost his immune system. Rhys has now been able to leave his sterile hospital room for a normal life.

* The world's only surviving all-girl sextuplets were born in Britain and celebrated their 21st birthdays last year. Hannah, Luci, Ruth, Sarah, Kate and Jennie Walton were conceived naturally, despite their mother Janet being told she could not have children. They were born at 32 weeks, within four minutes of each other.