A fertility organisation in Britain is saying that severely obese women should be barred from having National Health Service fertility treatment until they have lost weight.
According to new guidelines from the British Fertility Society (BFS), obesity reduces the chances that a woman will conceive naturally and decreases the possibility that fertility treatment will be successful.
The society says that those who are judged obese rather than severely obese should be "encouraged" to slim if they want fertility treatment and obese women could be banned from IVF until they lose weight.
The BFS says obesity increases the risk of complications during fertility treatment and pregnancy and endangers the health and welfare of both mother and child.
The society says it aims to work with patients to improve their chances of becoming pregnant with minimum risk to their health and that of their child and wants to see more resources for supporting and helping women to lose weight to improve their chances of conceiving.
The BFS recommends that women with a body mass index (BMI) above 35, which is severely obese, should have their treatment "deferred" until they have lost weight.
The BMI measure is a person's weight in kilograms divided by the square of their height in metres. A 5ft 4in woman with a BMI of 36 would weigh at least 15st.
The guidelines also recommend that women classified as obese, with a BMI between 30 and 35, should be encouraged to get below 30 before getting treatment.
The society says such women should be given help to lose weight, including psychological support, dietary advice, exercise classes and even weight-reducing drugs or gastric surgery.
Experts say even a moderate weight loss of up to 10 per cent can be enough to restore fertility.
The BFS guidelines which are used by fertility specialists, will be sent to all primary care trusts, which are responsible for paying for NHS fertility treatment.
However critics fear the guidelines will only serve to exacerbate inequalities which already exist between trusts in the granting of fertility treatment and make access worse.
The National Institute for Health and Clinical Excellence does not go so far as the BFS in stopping obese women from getting treatment.
Some experts say the recommendations are questionable, factually incorrect and based on bad science and it is more important to examine a range of factors and treat women as individuals.
They recommend that doctors adopt a flexible approach and look at cases on an individual basis; one obesity expert has called the new guidelines "discriminatory".
Obesity is thought to raise a woman's risk of miscarriage after IVF treatment.
Some 25% of UK women are said to be obese with a BMI of 30 or more.