Trans women will not be permitted to play elite women’s rugby for the foreseeable future because of ‘significant’ safety concerns, World Rugby has stated after releasing new guidelines for transgender players. In a statement explaining its decision, World Rugby said that after months of research and examining the latest scientific research it had “concluded that safety and fairness cannot presently be assured for women competing against trans women in contact rugby”. The Guardian first revealed in July that World Rugby was considering becoming the first international sports federation to adopt such a policy after finding “at least a 20-30% greater risk” of injury risk factors when a female player is tackled by someone who has gone through male puberty. In a document explaining its decision published on Friday, World Rugby said that “It is known that biological males (whose puberty and development is influenced by androgens/testosterone) are stronger by 25% to 50%, are 30% more powerful, 40% heavier, and about 15% faster than biological females. “That combination of mass, strength, power and speed means that in a direct physical contest, ciswomen in all these domains will be at significant risk of injury.” It added: “Studies suggest that the compounded or cumulative effect of these attributes may be even greater, with one study showing that punching power - a composite of mass, force/strength, and power is 160% higher in biological males than in biological females.” Previously it was thought that such advantages were negated when trans women lowered their testosterone levels to 5 n/mol for at least 12 months - which is the current International Olympic Committee policy applied across almost every sport. However World Rugby said that new research showed that they retain “significant” physical advantages over biological women even after they take medication to lower their testosterone. All trans women will still be able to play non-contact rugby against women, however. The guidelines also do not apply to trans women who have not undergone male puberty – as they will not have the gained the advantages of extra testosterone and androgens. It will also be up to each individual federation to decide whether to enforce the policy for the grassroots game. However in a statement explaining its decision, World Rugby made clear the potential added risk to player safety if countries went against its guidelines. “Given the best available evidence for the effects of testosterone reduction on these physical attributes for transgender women, it was concluded that safety and fairness cannot presently be assured for women competing against trans women in contact rugby,” it said. “As a result, the new guidelines do not recommend that trans women play women’s contact rugby on safety grounds at the elite and international level of the game where size, strength, power and speed are crucial for both risk and performance, but do not preclude national unions from flexibility in their application of the guidelines at the community level of the game. “Trans men are permitted to participate in men’s contact rugby.” Reacting to the announcement, Nancy Kelley - chief executive of LGBT rights charity Stonewall - said she was “deeply disappointed” with the news. “There is still a lot to learn about the impact of transition on athletic ability, but this does not mean that trans people are not already playing rugby or any other sport safely and fairly,” she said. “As the world continues to evolve, it is vital that policies expand rather than restrict any sport’s potential to grow and benefit all our communities. “We stand in solidarity with trans people across the world who’ll be disappointed by this news. We will do everything we can to make sport everyone’s game.”