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Lord Robert Winston
"There needs to be a debate about the use of gene technology"
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Saturday, 18 November, 2000, 00:07 GMT
Science screens out defective genes
ethan paget dunthorne - superhuman
Ethan was born healthy thanks to PGD
When Susan and Chris Paget Dunthorne's first baby died at the age of only four months, they had little hope of having a healthy child.

By the time their son Joshua was diagnosed with cystic fibrosis, doctors said there was nothing they could do for him.

But thanks to a new technique, pioneered at London's Hammersmith Hospital, it is now possible for people who carry defective genes to have healthy babies.

The technique, known as pre-implantation genetic diagnosis, allows doctors to select a healthy embryo to implant in the womb of the mother.

Inherited diseases such as haemophilia and cystic fibrosis can be screened out before the embryos are placed in the womb.

The BBC television series, Superhuman, has highlighted the success of PGD in Susan and Chris's case.

Joshua had been born weighing just over five pounds and the couple took him to doctors on a number of occasions before he was diagnosed with cystic fibrosis.

Common genetic defect

Cystic fibrosis is the most common genetic defect in northern Europe, and the CF gene is carried by one-in-20 of the population.

If both parents are carriers of the gene there is a one-in-four chance that a child will suffer from the condition.

New treatments mean that many people with CF live into adulthood, though daily physiotherapy, and drugs including enzymes and antibiotics are vital.

Joshua died aged four months
But Joshua died in his parents' arms at the age of four months.

Susan and Chris desperately wanted a second child but they were terrified that the same thing would happen again.

Although there is a test for CF, which can be done during pregnancy, the couple did not want to face the possibility of aborting a baby.

They consulted Hammersmith Hospital fertility expert Professor Robert Winston, who agreed to try PGD.

Although only 18% of PGD attempts are successful, Susan said: "We didn't really have any hope before - now we've got hope."

A large number of eggs are needed for fertilisation for PGD so Susan's ovaries were stimulated with a drug.

Fifteen eggs were collected in the operating theatre before being fertilised with sperm from Chris and placed in an incubator for three days.

egg under microscope - superhuman pgd
A large number of eggs are collected
Six embryos resulted, each invisible to the naked eye.

From the embryos, one cell was carefully removed for testing to see whether or not it carried the CF gene.

The technique leaves a hole in the side of the embryo but does not prevent the embryo growing into a healthy human being.

The Hammersmith's teams first attempt at genetic analysis of the embryos failed and it seemed that the whole process might be doomed to failure.

On the second attempt, conditions allowed them to determine that there were two healthy embryos free from cystic fibrosis.

Late at night, before the embryos were too old, Susan was taken to theatre and the embryos placed in her uterus.

Ten days later, a test was carried out to see if the embryos had implanted - itself a complex process.

hole after pgd test
Selecting a cell leaves a hole in the embryo
As Professor Winston points out, "humans are among the most infertile mammals on the planet".

Even with healthy eggs and healthy sperm there is no guarantee of making a healthy embryo and implantation can only occur during 48 hours out of every month.

But the embryo transfer in this case was successful and Susan was pregnant.

Healthy son

Professor Winston, who created the embryo, also delivered the baby - another son, Ethan.

"Technology allowed Sue and Chris to have a new baby son, confident that he doesn't have cystic fibrosis and that the heartache they previously suffered won't be repeated," said Professor Winston.

He acknowledges that the work may be controversial, and that the new techniques present many ethical dilemmas. But he believes that techniques like PGD hold out hope that the next generation of children will be able to lead a healthier life.

"One day medicine will change the destiny of children before they are even conceived," he said.

Superhuman - The Baby Makers is broadcast on BBC One on Sunday 19 November at 2110 GMT

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18 Oct 00 | Scotland
Couple angered by baby ruling
04 Oct 00 | UK
A design for life
04 Oct 00 | Health
'Designer baby' ethics fear
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