Six British couples have had healthy babies, whose sex they selected using a controversial technique to choose their baby's gender.

The children, the oldest of whom is now one, were conceived after their parents were referred by a UK clinic for the treatment in America.

All wanted to select the sex of their baby - so-called "family balancing".

Couples cannot obtain the Microsort treatment in Europe.

One North East couple had two boys and wanted a girl to complete their family.

An Irish woman, who already had six sons and whose mother had also had six sons, used the technique to have a daughter.

This is very dubious and not the way to go about having a family Nuala Scarisbrick, Life

Details of the cases were revealed at the American Society of Reproductive Medicine Conference in Seattle.

The Microsort technique, offered by the Genetics and IVF Clinic in Fairfax, Virginia, is 91% effective at producing girls and 74% effective for boys.

It costs �1,400, but the final cost can be between �4,000 and �15,000 after couples pay for insemination costs, scans or IVF treatment.

It involves marking the head of sperm with a fluorescent dye which attaches itself to DNA. They are then placed in droplets of liquid which are fired at 100 mph through a laser beam.

Sperm which will produce girls have more DNA and therefore more dye in their heads, allowing the laser to separate them.

Review

The clinic does not consider couples who do not already have children unless there is a gender-related genetic disorder in the family, such as muscular dystrophy, which is only inherited by boys.

Susan Black, formerly of Guy's Hospital, London, who now works at the clinic, told a national newspaper she was particularly touched by the case of a family from the north of England.

"It was a family who had three boys already and they very much wanted a girl.

"We were delighted to help them, and they now have a healthy baby girl."

In total, 300 babies have been born using the Microsort technique, 85% to couples wanting "family balancing". Four-fifths were girls.

Some couples have had terminations when sex selection failed.

Dr Paul Rainsbury, of the Bupa Roding Hospital in Ilford, East London, has sent couples to the US for the treatment.

Freezing

The Human Fertilisation and Embryology Authority (HFEA) in the UK is to begin a consultation next week over whether gender selection should be allowed in the UK.

Doctors told the conference also revealed details of a study of children up to the age of seven which showed the technique did not carry an increased risk of genetic abnormalities.

The Fairfax clinic has also demonstrated that frozen as well as fresh sperm can be used.

Ann Furedi of the HFEA said: "The new consultation will look at whether to allow gender selection of embryos and frozen sperm for social reasons in licensed clinics.

"It will also look at whether techniques such as Microsort which can be used before artificial insemination should be regulated by us."

At present, fertility treatments only need HFEA approval if the involve frozen or donated sperm or embryos or IVF procedures. Microsort does not.

But Nuala Scarisbrick of the charity Life, told BBC News Online: "This is making a child into a commodity that you can manufacture, choose and reject if you don't like it.

"This is very dubious and not the way to go about having a family, and there are bound to be even more abortions because there are bound to be mistakes."