She thought that this might mean sacrificing her dream of motherhood. For her, the news that a woman is pregnant having undergone embryo screening for the condition at University College Hospital, London, offers unprecedented hope.

“My mother had the cancer so we knew it was hereditary. I lost only one eye; some aren’t so lucky,” she said. “You do feel different and you do get picked on as a child. Even as a teenager, I decided that I didn’t want to risk having a baby who had to go through that.”

With chances as high as 50 per cent of passing on the retinoblastoma gene to a naturally conceived foetus, Ms Plowman, 33, and her husband, David, ruled out a normal pregnancy. “We began participating in embryo screening work at UCH but there were so many complications. Last autumn, after four years of trying, we began to consider the prospect of not starting a family.”

She then discovered that she had become pregnant naturally. “It was an accident and such a shock. I found out after nine weeks and had the amniocentesis test at 11 weeks to establish whether my baby had the retinoblastoma gene.

“Getting the test results was complicated and took two weeks. The wait was horrendous. I don’t know how people do it more than once. We probably would have had a termination if the result had been bad, but it is so hard. Fantastically, we didn’t have to decide.”

The Plowmans, who live in Bournemouth, are expecting a healthy baby girl early next month. Ms Plowman, a graphic designer, is going on maternity leave next week and is excited about becoming a mother.

“We do want more children, but only through embryo screening. The news that someone is successfully pregnant through UCH’s work is completely amazing. We will be in touch with the hospital soon to find out how our case is progressing. It gives David and me so much hope for the future.”

John Ramm was a baby when he lost both eyes to retinoblastoma. His daughter Bethan was 5 when she lost hers and had undergone four years of “hideous” treatment before doctors were forced to remove them.

But the 41-year-old musician says that he would not have gone through embryo screening even if it had been available. “My wife and I had no problems conceiving naturally. As I’m totally blind we decided that if our baby was blind it would not be the end of the world.” He suggests that IVF, which women have to undergo if they opt for embryo screening, “has its own risks”.

“I have three sighted daughters as well as Bethan, who is now 9, and although her illness has been hard on the whole family we have got through it. Bethan is near the top of the class at her mainstream school, and it has also brought us closer together.”

Mr Ramm, from Wrexham, North Wales, is a Christian and said that his faith does affect his approach to such topics. “I do object to screening — it’s pretty much in the same boat as abortion — although I don’t feel I have the right to tell anybody else what to do.

“But I am concerned that people with retinoblastoma might feel pressured to have this procedure, like people are pressured to have a termination if a condition is discovered during pregnancy. That personal decision has to be left to the individual, not a pushy doctor. The whole issue of genetic screening is a minefield.”

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