A US Olympic boxer has avoided a ban after claiming a failed drugs test was due to her having sex with her boyfriend.

Virginia Fuchs, 32, failed an out-of-competition urine test in February when it was found her sample contained two banned substances - letrozole metabolite and GW1516 metabolites.

But the United States Anti-Doping Agency (USADA) have now determined that the substances were transmitted through intercourse with Fuchs’ partner.

“The low amounts of letrozole metabolite and GW1516 metabolites detected in her sample were consistent with recent exposure to the substances via sexual transmission,” the agency revealed.

They added that Fuchs’ partner had been using the two substances for therapeutic reasons and found no reason to ban her.

“We strongly believe this case and others like it, including meat contamination and prescription medication contamination cases should be considered no violation,” USADA chief Travis Tygart said.

Under World Anti-Doping Agency (WADA) rules, the usual punishment for banned substances is a four-year ban.

Having missed out on a spot at the Rio Olympics in 2016, the exonerated flyweight fighter is now eyeing up a spot at the Tokyo Games in 2021.

“This has been a huge lesson for me and now that is over, I’m fully focused on preparing for Tokyo,” she said on Twitter.