A new clinic in Manhattan is appealing to British couples who want to pick the sex of their next child — a process that is banned in the United Kingdom.

Pre-implantation genetic diagnosis (PGD), which can reveal the sex of an embryo, is prohibited in Britain except when it is used to screen for genetic diseases.

The United States relaxed its regulations on sex selection in 2001 and American medical centres report interest from British patients who find out about their “family balancing” services through online advertisements.

Jeffrey Steinberg opened his New York clinic in January. Half of the embryos at present undergoing tests in his laboratory belong to British parents and four couples are already booked in for next month.

“Britain is far more conservative than it used to be. They were the innovators but now they’ve got handcuffs on,” Dr Steinberg said. “From a business standpoint, it’s the best thing going. From a medical standpoint, it’s a travesty.”

As recent healthcare debates show, many Americans balk at government involvement in medicine. Robert Brzyski, chairman of the ethics committee at the American Society for Reproductive Medicine, said: “The tradition in the US has been to not interfere with the reproductive choices of American citizens.”

The Genetics and IVF Institute in Virginia was one of the first medical centres in America to offer family balancing. Between 10 and 15 per cent of the 400 pre-implantation diagnosis cycles that it oversees each year come from abroad. Gary Harton, its PGD scientific director, said: “The people that want to do it will come and find you.”

Such medical tourism has boosted business for American doctors: the bill for procedures, travel and hotels can add up to £20,000. Most countries impose restrictions because of concerns that elective sex selection may facilitate cultural biases for male heirs.

Although evidence suggests that British patients tend to pick sons and daughters in roughly even numbers, most US clinics will treat only those parents who already have a child of the other sex.

Britain’s Human Fertilisation and Embryology Authority remains cautious, citing public opposition to sex selection. “In the US there is no official regulator to monitor clinics and no legal obligation to offer the counselling that is an important part of treatment,” a spokesman said. “Those who choose to go overseas for their treatment should make themselves aware of the laws and consider what impact there may be on any child that is subsequently born.”

The institute in Virginia takes pains to counter America’s reputation as the Wild West of reproductive technology. Patients go through counselling before the procedure and meticulous records are kept on the new babies. Mr Harton often reassures nervous British patients: “You’re no different to any other patient. You’re here to get what you want. To get a baby.”

Humans have tried to influence the sex of their children for centuries, since the Ancient Greeks tied off a testicle to have a son. But the only effective methods are PGD and Microsort, a technique that separates sperm bearing X or Y chromosomes before fertilisation. In PGD, a single cell is extracted from each IVF embryo before implantation. This is then analysed for the chromosomes that signify sex, allowing doctors to select the preferred embryo.

Stephen Wilkinson, a professor of bioethics at Keele University, believes that British regulations about the procedure should change. “The case for prohibition in the UK is not very strong,” he said. “The only people for whom there really is a ban are people who either can’t afford to circumvent the regulations or who don’t have the knowledge to do it.”

David Karabinus, a director at the Virginia institute, believes that elective sex selection will eventually be seen as just another form of reproductive medicine. “Just as there was an overreaction about IVF, there will be a gradual acceptance as we prove it’s safe. It’s there if people want it.”

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