Obesity is believed to negatively affect female reproductive health, it has been claimed.
Issuing guidelines on the issue, the British Fertility Society (BFS) recommended that all women should be advised to meet a weight appropriate for their height before becoming pregnant.
Additionally, those seeking fertility treatments should look to have a "normal" body mass index, with treatment delayed if it remains above 35, the society said.
Tony Rutherford, chair of the BFS's policy and practice committee, said: "Obesity reduces the chances that a woman will conceive naturally and decreases the possibility that fertility treatment will be successful."
It can also increase the chances of experiencing complications during fertility treatment, he added.
However, responding the society's guidelines, Dr Colin Waine, chairman of the National Obesity Forum, said that to deny treatment would be "discriminatory".
Mr Waine said that adopting such a stance would lead to "rationing" based on an individual's weight