Desiree Henry anchors the British 4x100m team (© Getty Images)
The USA are defending champions in this event, but so far the 2014 list is led by a 44.16 run by a Jamaican junior quartet in April.
A pair of speedy times in July from Trinidad and Tobago and Great Britain (44.23 and 44.66 respectively) established the challengers.
The USA will bring Kaylin Whitney and Ariana Washington from the 100m; the British will have Dina Asher-Smith and Desiree Henry at their disposal.
Parker Morse for the IAAF
