As was widely reported, the IAAF has issued new eligibility regulations for female classification, greatly impacting South Africa's Caster Semenya, among others.
In a press release on Thursday, the IAAF has amended their classification for an 'Athlete with Differences of Sexual Development' for five events - to be known as 'restricted events' - from 400m to the mile, including 400m hurdles races, 800m, 1 500m, one mile races and combined events over the same distances.
https://www.sport24.co.za/OtherSport/Athletics/iaaf-pass-new-regulations-semenya-forced-to-lower-testosterone-levels-20180426