World Rugby could ban transgender athletes from playing women's rugby, under a new proposal.
Rugby's international governing body says it has concerns over player safety.
A review into "rugby-specific transgender guidlines" has started in light of the "latest peer reviewed research".
World Rugby told the BBC there is a "clear safety risk when transgender women play women's contact rugby".
"Rugby is an inclusive and welcoming sport and World Rugby is fully committed to continuing to work with relevant groups to explore appropriate participation pathways for transgender athletes and is funding further research into the safe participation of all players in rugby."
The draft proposal, which was leaked to the Guardian, would still allow transgender men to play against cisgender men.
According to BBC, World Rugby's current policies around transgender players matches that of the International Olympic Committee.
Under the rules, transgender women must suppress testosterone levels for at least a year before competing. There are no restrictions for transgender men.
It would be the first international sports federation to ban transgender women from competing.