In the long argument over designer babies, did anyone imagine that parents might prefer a designer disability? While we were all worrying about the bionic offspring of the super-rich, two deaf lesbians in America were going round sperm banks, trying to make a deaf baby.

It sounds like the start of a bad joke, except that they have now managed it twice, thanks to a friend with five generations of deafness in his family. They claim that they are especially well equipped to look after a deaf child, which I am sure is true, and had they adopted one such child, or 20, we would all be praising their goodness.

The difference, of course, is that no child should be forced inside its parents' psychosis - whether they be from a hardline religious sect or Deaf Lesbians. The truth is that all of us have to contend with our parents, for good or ill, but at least we can't be committed at birth to spending the rest of our lives as circus performers or bank clerks, or missionaries. We have free will, and the great thing about growing up is personal choice.

What choice is there if your parents have already decided that you are going to be deaf, and that deafness will be your defining identity, just as it has been theirs? This is not the beauty of compatibility, it is genetic imperialism.

Deaf people, they say, have heightened senses, and a relationship to the world not shared by the hearing population. Fine, I have no trouble with that. But identity is going to be a big issue for the kids of the Deaf Lesbians, because both women belong to a radical group that defines deafness like blackness - not as a disability but as cultural difference.

My closest friend is black. She married a white man and their eldest child looks like an English rose - pale skin, blond hair, blue eyes. Nature does this kind of thing, and it is a celebration of difference and sameness all mixed up together. Nobody knows what kind of baby any two people will produce - and surely this is a blessing, not a bore? Must we control everything? If the answer is yes, we are paranoid. If either of the Deaf Lesbians in the US had been in a relationship with a man, deaf or hearing, and if they had decided to have a baby, there is absolutely no certainty that the baby would have been deaf. You take a chance with love; you take a chance with nature, but it is those chances and the unexpected possibilities they bring, that give life its beauty.

I am always on the side of risk, and always suspicious of control. The more controls we have, the less free we become. Parents usually try to control their children, and later their children hate them for it, while busily repeating the damage themselves.

How would either of the lesbians have felt if their own parents had said that heterosexuality was such a beautiful thing that they had to screen out any potential gay gene in their children, just to make sure they had a good life?

How would any of us feel if the women had both been blind and claimed the right to a blind baby? Even if we transform the language of disability into a dialectic of alternative functioning, should the medical system support parents who want their child to suffer a serious handicap?

We can make our world as friendly as possible for people with different physical capacities, but we cannot change the simple fact that it is better to have five senses than four, however enhanced the loss of one allows the others to be.

I believe that hearing, like sight, is a blessing, and if we are prepared to use technology to breed children we have deliberately disabled, it is not only the language of disability that will have to be radically reworked, but our entire moral perspective.

What this case suggests is that we can do what we like to our children, even if the consequences of our actions are irreversible.

As lesbians, the two women should know something about choice and personal freedom. They both practise as mental health specialists, so I hope they have a colleague who will be able to talk it through with two kids who turn up in 20 years, explaining that their mothers decided that they had to be deaf.