Chanel Brissett leads the world U20 lists with 12.75 – the second fastest time in history at U20 level – but the 18-year-old still missed out on a place on the US team for Tampere.
Brissett finished third at the US Junior Championships behind Tia Jones (12.89) and Cortney Jones (12.91) with Brissett missing out on a spot by 0.04, a time unmatched by non-US juniors in 2018.
Jones burst on to the scene two years ago at the age of 15, clocking 12.84 over the barriers. She went on to secure a place on the US team for the 2016 World U20 Championships in Bydgoszcz, taking bronze in the highest quality U20 race in history in 12.89 behind Belarus' Elvira Herman (12.85) and Jamaica's Rushelle Burton (12.87).
Jones, who also won gold in the 4x100m relay in 2016, will be looking to improve on her bronze medal in the individual event. She also won the Pan-American U20 title last year.
A big improver this year is France's Cyrena Samba-Mayela, who earned a silver medal at the World U18 Championships last year. Only 17, Samba-Mayela set a French U20 record of 13.00 on the road to Tampere.
The Jamaican challenge is headed by Amoi Brown who defeatedworld U18 champion Britany Anderson at the Jamaican U20 Championships last month, 13.09 to 13.19.
Steven Mills for the IAAF