The International Association of Athletics Federations has taken a dramatic step in regulating biological gender in track and field. 

According to a report from Endocrine Today, the IAAF will now require women with exceptionally high levels of testosterone to use a hormonal contraception for at least six months if they wish to compete in a number of different races.

The new rule was originally slated to go into effect back in 2018 but was suspended due to a pending decision from the Court of Arbitration for Sport.

The new rules will go into effect today, less than 5 months before the IAAF’s World Championships in Athletics, which take place Sept. 28-Oct. 6 in Doha, Qatar.

“Beginning May 8, if an athlete would like to be eligible for further competition in the restricted events, according to the rules, they should be able to prove that they have maintained their testosterone level below 5 nmol/L for 6 months,” Stéphane Bermon, director of health and science for the IAAF, told Endocrine Today“We have our world championships at the end of September this year, which is a bit less than 6 months from now. We have some exceptional measures for this event. If athletes started suppressive treatment and can show that by May 8, they already have testosterone levels below 5 nmol/L, and they maintain the testosterone level below 5 nmol/L until the championship event, then they could be eligible.” 

The ruling was in response to a complaint filed in June of 2018 from South African athlete Caster Semenya and Athletics South Africa, which argued that the new rule was “discriminatory, unnecessary, unreliable and disproportionate.” The IAAF argued that it does not infringe on any athlete’s rights, including the right to equal treatment, but instead is a justified and proportionate means of ensuring consistent treatment and preserving fair and meaningful competition within the female classification. 

Andy Berg is Executive Editor of Athletic Business.