A controversial service that "guarantees the sex of your baby or your money back" has given new meaning to the term "family planning" for UAE parents. The Selnas method, developed by French cellular biologist Patrick Schoun in the early 1990s, purports to tell women on which day of the month they will conceive a boy or a girl.

The service claims an international success rate of over 95 per cent in more than 20 countries. The system does not require invasive surgery, dietary changes or drug treatment, but relies instead on conception timing and establishing the patterns of a recently discovered alternative ovulation cycle.

The 12-month programme costs Dh300 and if results do not produce the desired bouncing baby boy or girl, disappointed parents can claim a refund. Dr Naghmeh Karbasi, an Iranian paediatrician based in Dubai, is the only practitioner in the UAE allowed to offer the service, which has been approved by the Ministry of Health.

"New research shows that every month, for up to eight days at a time, the egg omits a positive and negative charge," Karbasi said. "The type of charge given out depends on which sperm will succeed in conception - and it is the sperm which decides the sex of the child.

"The Y chromosome sperm which produces a boy is attracted to the ovum's negative charge, while the X chromosome sperm for girls needs a positive charge. "The system is extremely successful because a Y chromosome sperm cannot initiate conception if the ovum is positive, and vice versa."

Karbasi said establishing the cycle in a patient requires careful questioning. "Every patient taking part in the programme needs to fill out a questionnaire documenting their blood group, menstrual cycle and details of previous pregnancies.

"The form is then sent to a laboratory in France where the individual's cycle is worked out. The patient then receives a 12-month calendar which gives them the dates on which they are most likely to conceive their preferred-sex child. Each calendar is unique and will only work for that patient."

The controversial nature of the treatment may cause concern in some communities where boys are favoured over girls, but Karbasi said that so far, requests among national women have been weighted in favour of females.

"I am already treating several women here, and at the moment, most of them want daughters," she said. "It's not really a case of women here wanting to produce sons because in today's society, parents generally want balance. Because of financial constraints and working mothers, most people don't want huge families, but do want children of both sexes."

However, Dubai gynecologists are sceptical of the new method and the ethics of choosing the gender of a baby. Dr Janaki Gopalan, Specialist Obstetrician and Gynecologist at the Welcare Hospital, said, "I do believe these methods have a certain amount of success - and have seen them work - but scientific evidence as to why is not conclusive.

"I am also not in favour of gender selection because it could cause an ecological imbalance in the human population. "In this part of the world there is pressure to produce boys, and in time such practices could upset the balance. A healthy attitude to family planning is when a baby is wanted, no matter what its sex."

Dr Tina Gai, an obstetrician and gynecologist at the American Hospital, firmly opposes the idea. "Unless artificial insemination is used, the chances of having a girl or a boy are 50-50," she said.

"I don't believe people should try to determine the sex of their child because there are serious implications. India is one example where the culture has meant the balance of nature has been upset. There are now laws in place to prevent gender determination practices because of it."

Karbasi defended the Selnas method: "In this day and age, it's simply not practical to keep on producing until you get a boy or a girl. It can be a financial burden on the whole family, as well as being physically, mentally and emotionally draining for the mother.

"Previous methods for sex selection don't have such a high success rate, and include invasive techniques which are unpleasant for both parents. Often they also raise ethical questions and are very expensive.

"One of my patients who has seven sons is desperate for a baby girl, and her case is not unusual. Ultimately you can't go on trying forever, hoping that one day you'll get lucky."