The result of Caster Semenya’s landmark case against athletics’ governing body will be published on Wednesday.
The double Olympic 800m champion is challenging the IAAF over its regulation restricting testosterone levels in female runners.
The rule will apply to women in track events from 400m up to the mile.
Semenya would either have to take medication to be eligible to compete in the 800m, change events or move to compete against men.
The Court of Arbitration for Sport says it will publish its ruling at midday tomorrow.
Semenya won 5,000m gold at the South African Athletics Championships on Friday – a new distance for her that would not be affected by the IAAF rule change.
She has described the IAAF’s new rules as “unfair” and said she wanted to “run naturally, the way I was born”.
The rules would require athletes to keep their testosterone levels below a prescribed amount “for at least six months prior to competing”.
The IAAF said in April 2018 that the new measures would stop women with high testosterone levels gaining a competitive advantage.
Testosterone is a hormone that increases muscle mass, strength and haemoglobin, which affects endurance.
The rules were intended to be brought in on 1 November 2018, but the legal challenge from Semenya and Athletics South Africa caused that to be delayed until 26 March.
The United Nations Human Rights Council has called the plans “unnecessary, harmful and humiliating” and South Africa’s sports minister called them a “human rights violation”.