Ashley's parents call her their Pillow Angel, a moniker that is a reference to the love and joy they feel for their nine-year-old daughter and the severe disabilities she has suffered from birth. She cannot sit up, walk or talk, is fed by tube, and, as her parents put it, "stays right where we place her - usually on a pillow".

Ashley won't know this, as she is brain-damaged and has the awareness, her doctors say, of a baby, but she has become the subject of a passionate argument in disability circles and beyond. Her name is becoming synonymous with the debate about the acceptable limits of medical intervention in the care of disabled people.

The cause of the controversy is the "Ashley Treatment" - a course of surgery and hormone supplements devised for her at her parents' request and with the blessing of doctors - that will for ever keep her small. It involves surgical operations, including a hysterectomy, and hormone prescriptions that will, in effect, freeze-frame her body at its current size.

Although she has a normal life expectancy, she will, physically, always be nine years old. Her growth has been suspended at 4ft 5in (1.3 metres), rather than the 5ft 6in she would probably otherwise have become. Her weight will stick at around 75lb (34kg) rather than 125lb.

This week Ashley's parents, who have chosen to remain anonymous and have only let it be known that they are "college-educated professionals" living in Washington state, have posted on the internet a lengthy explanation of their desire to stunt her growth. It is the first time they have given a public account of their actions. The explanation is accompanied by a gallery of photographs showing Ashley over the years, from her as a smiling baby a few months old, through to today when she is seen nestled in a sheepskin rug.

She was diagnosed, they explain, with brain damage with unknown causes just after birth and has remained at the same developmental level since about three months. Three years ago she began to show early signs of puberty, and they grew anxious about the impact of fertility and of her rapidly increasing size and weight on the quality of her life. In discussions with doctors at Seattle Children's hospital they devised the treatment: removal of Ashley's uterus to prevent fertility, excision of early buds on her chest so that she would not develop breasts, and medication with high doses of oestrogen to limit her growth by prematurely fusing the growth plates of her bones.

The parents insist that the treatment, carried out in 2004, was conceived for Ashley's benefit and not their own ease or convenience. With a lighter body and no breasts, Ashley will have fewer bed sores and lie more comfortably. And a smaller Ashley can be cared for and carried. "As a result we will continue to delight in holding her in our arms and Ashley will be moved and taken on trips more frequently instead of lying in her bed staring at TV or the ceiling all day long," they write.

But as news about the treatment became known, Ashley's parents were surprised by the virulence of some of the response. Comments on chatboards have included: "Ouch - this smacks of eugenics"; "I find this offensive, truly a milestone in our convenience society"; "This smells, I can't agree with this".

Outrage has also been expressed by organisations representing disabled people across the US, with many asking why a course of treatment that would not be countenanced for an able-bodied person should be allowed in this case. "People have been horrified by the discrepancy," said Mary Johnson, editor of Ragged Edge, an online magazine for disability activists.

She said she felt for Ashley's parents and could understand why they had made the decision. But she feared that the treatment would open a Pandora's box that could have adverse effects for other children. "What will now be said in the case of a child with spina bifida, who you could argue has the same physical challenges but whose brain is fully functioning? This is very troubling."

Debate has raged among doctors and medical ethicists. Jeffrey Brosco of Miami University has co-written an editorial in the Archives of Pediatrics & Adolescent Medicine criticising the procedure as an experiment without proper research controls. "This is a technological solution to a social problem. I work with severely disabled children and know how hard it is on families, but what we need most is better federal funding so that they can be cared for properly."

State help for caring for disabled people is available through Medicaid, which is restricted to poor families. Ashley's parents would not qualify, and say it is impossible to find carers they can afford.

The ethical row is likely to deepen as the Seattle doctors, led by Daniel Gunther, say they are considering other children for similar treatment, though only after monitoring by the hospital's ethics committee. The doctors accept that Ashley's hysterectomy was contentious, given the dark history of sterilisation of disabled people in Europe and America, and that there were risks involved in the operations and oestrogen doses.

But they argue the benefits outweigh the risks. Ashley has, they admit, been "infantilised" but question the harm that would do a person whose mental capacity "will always be that of a young child".

Ashley cannot say what she thinks. But in a telephone interview with the Guardian last night, her father said that many people had assumed he and his wife had to agonise over their decision.

"We didn't. It was easy," he said. "We clearly saw the benefits to Ashley's quality of life. We have also been criticised for harming Ashley's dignity. But for us, what would be grotesque would be to allow a fully formed woman to grow up, lying helplessly and with the mentality of a three-month-old."

Hormones

There is a long history of hormones being used to control growth in children. In some cases they are used to counteract a hormonal imbalance or genetic disorder. But there have also been sustained attempts to control body size for cosmetic reasons.

In 1956 MA Goldzieher became the first to report using high doses of oestrogen to treat exceptionally tall girls. Over ensuing years thousands of tall girls were prescribed oestrogen to prevent them tipping over the 6ft mark, protecting their marriage prospects. As the stigma against tallness in women has declined, so has the practice, though it still continues.

Boys considered to be shorter than the norm have recently begun to be treated with a growth hormone, often for cosmetic reasons. US federal restrictions have been loosened, allowing private paediatricians to offer the treatment that can cost up to $40,000 a year.

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