World Rugby is set to become the first international sports federation to ban transgender women from competing, citing safety concerns.
Under current regulations, transgender women are permitted to play women's rugby if their testosterone levels are lowered to the amount enforced by the International Olympic Committee.
But after conducting areview, World Rugby's research showed allowing transgender women to participate in women's contact rugby posed a "clear safety risk".
As revealed by The Guardian, World Rugby found there is "at least a 20-30 per cent greater risk" of injury when a female player is tackled by someone who has gone through male puberty.
World Rugby's research also found transgender women retain "significant" physical advantages over biological women after taking testosterone medication.
Specifically, transgender women "are stronger by 25 to 50 per cent, are 30 per cent more powerful, 40 per cent heavier, and about 15 per cent faster" than players assigned female at birth, according to the report.
In a statement to BBC Sport, World Rugby confirmed: "The latest peer-reviewed research confirms that a reduction of testosterone does not lead to a proportionate reduction in mass, muscle mass, strength or power. These important determinants of injury risk and performance remain significantly elevated after testosterone suppression.
"This presents a clear safety risk when transgender women play women's contact rugby and this position is reflected within draft guidelines that are currently out for stakeholder consultation prior to the World Rugby Council considering the matter later this year.
"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. This is in addition to extensive non-contact participation avenues that are available to everyone at union level."
A final decision is not expected to be made until November's World Rugby Council meeting.
Landmark World Rugby transgender workshop takes important step towards appropriate rugby-specific policy pic.twitter.com/9D1mK3Wr2r
Dr Nicola Williams, director of women's rights advocacy group Fair Play for Women, praised World Rugby for their "bravery".
"The sensitivity around this issue around transgender issues, and the fear that people would be called transphobic for raising concerns has meant that most sporting bodies have buried their head in the sand on this," Williams told BBC Sport.
"So World Rugby must really be commended for their bravery and integrity, for tackling this head on and following a science-based approach."
But Loughborough University medical physicist and transgender woman Joanna Harper, who attended World Rugby's transgender workshop in February, opposed the ban.
"Putting restrictions on trans-women is a reasonable thing to do, but I certainly don't agree with this idea of an outright ban," Harper told BBC Sport.
"I don't think this is necessarily the way to go. World Rugby has given us a month to issue responses and I will do so."
"If you think of New Zealand, if you think about our communities, we'd like to think we are a little unique from everybody else. But also, the formats of the games that we play that we offer also have to be taken into consideration.
"For us, it's really the start of us taking that document and now coming up with what we think is an appropriate policy for us in New Zealand.
"We may have different or tailored guidelines for us here in New Zealand, we just don't know what the guidelines will be.
"The situation is quite complex, but I'm really proud that we're having a conversation ... and we're trying to find ways that trans athletes can be involved in our sport."
