Women and girls in the UK transitioning to become men should be able to have their eggs frozen by the NHS, the British Fertility Society has said.
Current guidance says cancer patients should be given the chance to preserve their fertility before undergoing treatment that can make them infertile.
But the BFS said transgender patients and women whose medicines can make them infertile should also be included.
The provision of fertility preservation treatment was "patchy", it said.
Fertility preservation for those transitioning to a different sex is routinely paid for by the NHS in Wales and Scotland.
But in England there is a postcode lottery over who receives it because it is funded locally by clinical commissioning groups, which have different rules over who is eligible to receive it.
Dr James Barrett, lead clinician at the gender identity clinic at Tavistock and Portman NHS Foundation Trust, said the number of people coming forward with gender dysphoria – where a person experiences discomfort or distress because of their biological sex – had increased "rapidly" over the past decade.
But he said NHS funding for fertility preservation for this group had "yet to catch up" and they were not always able to self-fund for the treatment.
Hormone therapy and surgery for those with gender dysphoria often leaves them infertile.
"We're in a peculiar position in that a proportion of the trans people in the country – Wales and Scotland for example – will routinely have preservation funded, whereas some patients in England will have it funded by the NHS and others will not," Dr Barrett said.
"The question on whether to fund it at all to some extent is a kind of social and political question."
Freezing eggs, embryos, or ovarian tissue can give transgender people the opportunity to have a child who is biologically related to them through pregnancy or surrogacy.
The BFS's new guidelines, published in the journal Human Fertility, cover fertility preservation treatment for medical reasons for women in the UK.
Fertility preservation treatment includes the freezing of unfertilised eggs and embryo preservation, as well as the freezing and transplantation of ovarian tissues.
The National Institute for Health and Care Excellence (NICE) released guidance in 2013 on fertility preservation treatment for cancer patients, whose medicines – such as chemotherapy and radiotherapy – can leave them infertile, but it did not mention others at risk of infertility.
The BFS's new guidelines says treatment should also be discussed with other patients about to undergo treatment that can potentially cause infertility.
This also includes girls and women with conditions they are born with, and those who undergo stem cell transplantation for reasons other than cancer, such as for sickle cell anaemia.
In the UK, about 7,000 women aged 15 to 39 are diagnosed with cancer each year, and many of them will need cancer therapies that will affect fertility, the BFS said.
It estimated that a proportion of these women – in the "low thousands" – might want fertility preservation treatment, but currently a number in the "low hundreds" were receiving it.
It costs about £5,000 to freeze eggs and embryos and £300 a year to store them.
Prof Adam Balen, chairman of the British Fertility Society, said: "There are a number of situations where the preservation of fertility is needed.
"This has to happen at a time before a person is ready to start a family and can sometimes be the only hope for becoming a parent in the future."
NHS England said the funding of the treatment was a matter for clinical commissioning groups.
NICE said it had no plans to update its own guidelines on fertility "at the moment".
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