Just one look at twins Zoe and Kira is enough to see they are full of life and the very picture of good health, just a few weeks after celebrating their first birthday.

It is a joyful scene for any proud parents but one that is particularly precious to David and Rachel Underhill.

Exactly a year ago these same twins were fighting for life in an incubator at Royal Sussex County Hospital in Brighton after being born nearly ten weeks premature.

Kira weighed 3lb 8oz while Zoe was even smaller at only 3lb 1oz.

But the problems for the family were only just beginning after the couple told their doctor they were Jehovah's Witnesses and would not allow blood transfusions to be given.

Rachel, an accounts manager, was due to give birth in late September last year but unexpectedly went into labour on July 24 while at work.

Rachel, 25, and David, 40, were rushed to hospital where they were promptly informed there were not enough trained staff available at the Trevor Mann baby unit to care for the twins after birth.

The couple, of Canada Close, Telscombe Cliffs, were told a helicopter would take them to a hospital in Swindon instead until Rachel's consultant pointed out there was not even time for that. Further complications convinced doctors Rachel would need a Caesarean operation within the next half hour.

She said: "It was all a bit of a panic. I didn't expect to give birth for another few weeks and wasn't prepared. Our midwife hadn't told the doctors we were Jehovah's Witnesses so it was a real shock when they said I would need this operation.

"When I refused to have a blood transfusion they weren't very understanding at first because time was running out. The anaesthetist told me 'if you don't have blood, you realise you are going to die.' I replied it was my religious conviction."

There are around 500,000 Jehovah's Witnesses in the UK and more than five million worldwide. Followers accept medical and surgical treatment but they also believe blood transfusion is forbidden for them.

Witnesses refer to Biblical passages such as: "Abstain from . . . fornication and from what is strangled and from blood" (Acts 15:19-21), and "Only flesh with its soul - its blood you must not eat" (Genesis 9:3-4).

While these verses are not stated in medical terms, Witnesses view them as ruling out transfusion of whole blood and plasma.

Rachel said: "It's quite complicated but we believe you should not take out people's blood and put it into our blood because it would contaminate us.

"We consider blood to be very important because it is what Jesus gave us as his ransom to save mankind. I have been brought up as a Witness and it is something I have always believed in. I have grown up with it."

In the end staff at the Royal Sussex were able to operate on Rachel without a blood transfusion by giving her high boosts of iron instead. Yet the same treatment could not be offered to the twins.

In the first few days of the Zoe and Kira's lives, doctors told their parents the girls were so premature they would not be able to make their own blood marrow, which builds up the white cells to make more blood.

It was at this point the family called on the services of Dennis Cave, a member of the Jehovah's Witness medical liaison committee, who came into the hospital to work on the family's behalf.

He was able to present to doctors a selection of medical articles about the use of non-blood alternatives which could be prescribed instead.

As a result the twins were put on a drug called erythropoeitin or epo, a hormone which stimulates bone marrow to produce more blood, which was administered on a daily basis for the next five weeks.

Within a few weeks the epo began to have a substantial effect on the twins and doctors realised there would be no need for transfusions.

Rachel said: "The doctor was so impressed he told us if he had his way all premature babies would be prescribed epo.

"The only problem is that it's too expensive for the NHS to use as an alternative to blood except in exceptional cases."

Kira and Zoe stayed in hospital for six weeks and came home on September 6, three weeks earlier than expected due to their recovery on epo.

The family's experience with the twins has convinced them they did the right thing but they insist they would have done the same if things had not gone so smoothly.

Rachel added: "It all happened so quickly we didn't have a chance to discuss it but both David and me feel the same. Our beliefs are very important to us and we put faith in our God that he would look after us all.

"We never thought there would be a risk to our twins because we knew there were modern techniques available.

"But we realise if something did go wrong we would have risked losing the babies."

Dr Neil Aiton was the consultant neo-natologist responsible for the twins at the Trevor Mann Unit.

He said: "There is still some debate as to whether epo is helpful during the natal period but it definitely seemed to be effective with these twins.

"I must admit it was a surprise to me and it has certainly contributed to our understanding."

He said the situation with the Underhills was very rare and in all his years as a doctor he had only dealt with Jehovah's Witness patients on less than a dozen occasions.

"The interesting thing with children is how parental views should impose upon the care of children.

"There's a very real ethical issue here.

"We would always try to meet parental wishes but if we felt there was a medical danger to the child we would take it to the courts. This has happened in the past."

Today both twins are doing well although, because they were so born so early, they are still small for their age and continue to need regular check-ups at the unit.

Rachel said: "They are two very active one-year-olds and we're very proud of them.

"We wanted to tell our story so people could not say Jehovah's Witness children will die if they are not given blood."