One in three couples who pay hundreds of pounds to choose the gender of their child at a controversial London fertility centre are ending up with a baby of the opposite sex.
The London Gender Clinic, which opened three years ago is said to have estimated that its success rates are "more than 50 per cent but less than 70 per cent".
The Labour peer Professor Lord Winston, head of fertility studies at Hammersmith Hospital, has tested the Ericsson method that the clinic was using until a few months ago and said that results had shown an "exactly 50-50" chance of getting the sex of your choice.
The system was developed in 1973 by an American scientist, Dr Ronald Ericsson, and relies on the physical differences in the swimming ability of the male and female sperm, which are said to separate at different rates. The sperm are laid on top of a solution and the male ones supposedly reach the bottom of the tube more quickly than the female ones.
Parents who go to the London Gender Clinic, set up by Dr Peter Liu, a biochemist, and Dr Alan Rose, pay pounds 650 for a first treatment with reduced fees of pounds 400 for a second and pounds 350 for a third. It refused to comment this week.
The Human Fertilisation and Embryology Authority has no powers over the clinic because they do not use donor sperm and no sperm is stored there.
The HFEA believes sex selection techniques are "acceptable for medical reasons where a woman is at risk of having a child with a life-threatening disease", but adds: "The authority is persuaded by the arguments against sex selection for social reasons and this view is strongly supported by the public."
Dr Peter Brinsden, medical director of Bourn Hall, the pioneering IVF (in vitro fertilisation) clinic where Louise Brown, the first test-tube baby, was created, said: "It is perhaps chance more than anything else. Technology is not advanced far enough to get respectable success."
He added that he would be in favour of the HFEA bringing sex selection clinics with its remit.
A spokesman for Issue, the national fertility association, said it was "totally opposed to sex selection of embryos except in circumstances of genetic illness which runs in the family".
He added that he was happy that the HFEA had taken a strong stance against it, but wished there were stronger guidelines banning clinics from offering such procedures.
Lord Winston who will be speaking on the subject in his maiden speech in the Lords this week,is calling for legislation to be tightened up so that those who are not medically qualified in this area can offer treatments. "There is no evidence [gender selection] works at all," he said. "There is a need for us to look at this loophole in the law where people who are not medically qualified can give medical treatments."Reuse content