Somewhere in Thailand a baby boy is in hospital fighting off a lung infection unaware that he is at the centre of an international media storm.

Nearby is his surrogate mother. She is telling the world's media how his parents deserted him. Several thousand miles away In Australia they are bringing up his twin sister. They say they didn't know until now that another child existed. They didn't abandon him.

Meanwhile, well-meaning people from across the globe have donated £110,000 (at the time of writing) to help with his upbringing.

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And this muddle and contradiction is because the baby boy, Gammy, has one extra chromosome. He has Down's syndrome. Gammy looks sweet but he isn't the perfect child his Australian parents craved.

His fate begs the question: what is perfection in a child?

There is an uncomfortable sense of the corruption of affluence, of the Australians being morally inferior to the impoverished Thai women. She claims they demanded an abortion when they were told of the boy's condition. She refused, saying it was against her religious principles. Then, after the birth, she claims they just left him behind.

In her version of the story, the son was treated as if he was a commodity for which the Australians had gone shopping. He was damaged goods so they didn't take him.

It is easy to vilify them from the safety of our accepting society. We need to acknowledge our attitude to disability has travelled a great distance in a generation.

Even when my children were babies I can recall people saying the only thing to do if you had a disabled child was to have it institutionalised immediately. Anything else would be 'unfair' to your other children.

Then, as now, it sounded barbarous to my ears. But throughout the 20th century it was commonplace in the UK (and elsewhere) to place children with any physical or mental disorder out of sight. They lived in hospitals or homes and attended special schools.

In 1913, just a year before the war we are remembering, 40,000 men and women in Britain were deemed 'feeble minded' or 'morally defective' and were locked away under the Mental Incapacity Act. They were placed in institutions. We can now shudder at their fate, at the abuse many of them must have suffered.

Because their disorders were not understood, they were treated as second-class citizens, barely citizens at all. They were given neither affection nor empathy. They were robbed of dignity and autonomy.

There are horror stories aplenty. I'll mention one. Between 1942 and 1954, 10,000 leucotomies were performed. That's a procedure that cuts the connections between the frontal lobes and the rest of the brain. Can you imagine?

It's the stuff of nightmares. Too often the sick or disabled were abused by the medical or caring professions, backed by a society that preferred to be left in ignorance of what was going on.

My point is that the moral high ground has always been a precarious place in issues such as these. It continues to be. For example, can any of us really be complacent about the support, funding or facilities for the disabled in Scotland?

We might tune into The Pursuits of Darleen Fyles on Radio Four and applaud the fact that the main characters are played by actors with learning disabilities, that the script is based on true stories and partially improvised.

But the mere fact that we report it flags up its rarity.

Life is still tough for people with disabilities like Down's syndrome. For every one who acts or paints successfully, a dozen are unemployed and isolated.

Don't we all know there's more that should be done, that we can do? Where does that knowledge leave us on the moral spectrum?

If the Australian couple did run away from their responsibilities to their son, they were recklessly negligent and cruel. However, their fear and denial will be recognised by many new parents confronting disability for the first time.

The surrogate mother Patteramon Chanbua seems to have a more humane approach. She says she loves little Gammy and is willing to bring him up. A cynic might suggest that £110,000 will sweeten that pill; that in terms of financial security, Gammy might be the best thing that ever happened to her?

But there is also a sense that her Buddhist faith gives her a deeper understanding of what matters in life. She may have been willing to carry a baby to make money. She wasn't willing to abandon one. She didn't demand perfection.

We now live in a complicated world where a baby may have three parents. Rates of surrogacy are said to have risen 500% in Australia alone. Couples with infertility problems, other health difficulties or couples who are gay can, at a price, have a child.

There are also developments in the field of genetic modification.

Legislation that will pass through Westminster in the autumn could make Britain the first country in Europe to permit a three parent fertility technique that is - according to Dr Robert Winston - genetic modification.

It involves removing mitochondrial DNA from an egg or embryo and replacing it with the DNA of a donor. The procedure will allow people with a high risk of passing on conditions such as muscular dystrophy to have children without the defect.

No doubt we will see much debate about it being the thin end of a wedge.

Designer babies could be the next step. Will we be able to order up the perfect child - tall, blonde, blue-eyed - as though we are choosing from a take-away? No more waiting to see whether nature has thrown up granny's nose and daddy's knees.

No more leaving it to the lottery of nature.

A woman once wrote to the playwright Bernard Shaw protesting that with her looks and his brain they could make the perfect child. He is said to have replied what if it has my looks and your brain? A genetic pick and mix would have offered them a solution.

Or would it?

However clever the scientists get, can they ever promise so-called perfection? A child bred to have the body of Elle McPherson, the face of Nigella Lawson, the speed of Jessica Ennis-Hill and the brain of Mary Beard might also be a spoilt and selfish character.

And isn't it character that matters the most?

There, I think, is one of the moral lessons of Gammy. If the Australians chose to leave him behind because of his disability, they used the wrong measure.

Gammy's fate demonstrates the need to tighten up on international surrogacy before we take another step along a path to hi-tech eugenics. As in nature, parents should take whatever comes.

We might banish syndromes like Down's. We might dispel the extra chromosome forever. But we might be no nearer to producing the perfect child. Those who might try to buy themselves some kind of guarantee should think again.