Adam Rose went for a walk with his parents one morning when he was eight. It was to be a life-changing outing. Holding his hands, they told him his father was not his "real father". He had been conceived using sperm inseminated from a man he would never know.
That day in Wimbledon Park, south-west London, has stayed with Mr Rose as though it happened yesterday. "I felt like a freak because no one else in my perception had been conceived in that way and it was something that nobody had heard of. It was very shocking," he said.
Mr Rose's conception, known as donor insemination, or DI, was the only infertility treatment available in 1967, 11 years before the first test-tube baby was born.
"My mother just turned to me and said, 'Your father is not your real father but he is still your daddy and you mustn't tell anyone.' She told me that I could never find out who my real father was, so not to bother asking any questions. It took me years to realise how I felt, and how devastating the news was. I started thinking that everyone could be related to me," he said.
Mr Rose, who is 33 and works as a conservation biologist, now knows he was conceived in a private clinic in Harley Street, central London. But he has not been able to find out anything about the identity of his genetic father or his ethnic roots, and believes he suffers from an identity crisis. "My conception using DI [donor insemination] has none of the glory of test-tube babies or advanced medical techniques. It has been used for thousands of years to breed pigs." He said his priority is to find out which country his father was from. "But I have found I have no human rights at all in terms of my genetic identity."
Mr Rose, who is about to become a father himself, added: "My mother is blond-haired and blue-eyed, but I am small and dark, and could come from the Middle East. I now know I could have as many as 200 half- brothers and sisters."
One half-sister, Joanna, was brought up by the same parents. Ms Rose is a 27-year-old graduate student studying social work. She said she had always felt something was "not right" and asked lots of questions about why she did not look like her brother.
She said: "I am desperately unhappy that I have no information about where I am from, my medical history, my ethnicity, 50 per cent of my biological family ancestors and heritage. This has caused me immeasurable pain and suffering and needs rectifying." Ms Rose took genetic tests with two people she believed may have been her biological relatives.
There is agrowing number of children demanding the right to know who is their genetic father. They were both born before the establishment of the Human Fertilisation and Embryology Authority (HFEA), which licenses all fertility clinics in Britain and keeps records of all sperm and egg donors. Since 1991, more than 11,000 DI children have been conceived in Britain. Their details are registered but not available.
According to new findings from one of the first studies of the views of DI adults, people conceived in this way feel it is an infringement of their human rights to be denied the information. Almost 90 per cent believe DI children should be told before they are 10 years old, but most are told at an average age of 24 years.
The study, published in the latest issue of The British Fertility Counselling Journal, reports that DI children feel as though a secret has been withheld from them from an early age. Half said they had suspected they were not related to their father before being told. Three out of five said the "secret" had had a strong influenced on them before they were told about it, the majority believed they had the right to find out who their genetic father was, and 58 per cent wanted to meet him.
Children who were conceived using donated sperm appear to be experiencing feelings similar to those felt by adopted children 25 years ago.
In the mid-Seventies, thousands of adopted children demanded to be told their genetic history and were provided with details of their background. Many traced their genetic mothers with the help of counsellors who acted as intermediaries, even though the birth mothers had been promised they would not have to reveal their identity when they gave up their children for adoption.
Dr Alexine McWhinnie, a senior research fellow for the social work department at the University of Dundee, who believed DI children felt "almost identical" to adopted children in the 1970s, said it was unacceptable that the information about their parents was not available, despite the creation of the HFEA.
"We can't go on treating these people as babies. They are adults with minds of their own, and we need to respect their autonomy. It is unrealistic to expect that they tolerate this," Dr McWhinnie said.
She claimed that the medical profession was unfairly putting pressure on parents who chose to have children with donated sperm. "It should be recognised that this is not the same as natural parenting but parenting with an extra hard task," she said, suggesting the potential problems were putting people off DI.
Concern has grown about the possible negative effect on family relationships caused by keeping a child's origin hidden.
However, work done by Susan Golombok, a professor of psychology and director of the Family and Child Psychology Research Centre at City University, London, has found that children conceived with donated sperm experience no more significant psychological problems than children brought up by their genetic parents, suggesting that the absence of a genetic link with the father makes little difference.
But she is cautious about the results. "It is important to remember that the oldest children studied were only eight years old and not one of them had been told that he or she had been conceived using the sperm of an anonymous sperm donor.
"It remains to be seen what happens to these children as they grow up, particularly as they reach adolescence. This is the time that children become concerned with issues of identity and begin to have more difficult relationships with their parents," she said.
Her findings are supported by Barry Stevens, 47, and Janice Botsford, 52, siblings who were conceived by donor insemination and brought up in Canterbury, Kent. They said they had a loving and supportive upbringing and had not suffered from any significant emotional problems. They were both told about their conception six months after their social father's death, when Mr Stevens was 18.
Both believe they have a right to find out more about their biological father, and want to see the system changed so that families are able to be frank with their children. They have only recently found out that they both have the same two parents, even though they were born five years apart.
Although most countries keep sperm donation anonymous, children in Sweden are allowed to find out who is their genetic father after their 18th birthday. In New Zealand, many clinics advise parents to be open with their children and recruit donors who are willing to be identified. Sperm donation clinics in California now ask men if they are willing to be identified - 50 per cent agree and 85 per cent of future parents choose these donors.
From the DI adults who have spoken out for the first time, it is becoming increasingly clear that fertility treatment is as much about the rights of the child as it is about helping infertile couples to produce offspring.Reuse content