Tournament chief executive Rachael Carroll said it was "a real shame" and the postponement was "a very tough call".
"We've considered many scenarios for 2019 but, unfortunately, we haven't been able to come up with a viable option."
The potential impact of the world cup on player availability was a factor that could not be ignored, Ms Carroll said.
"While that is disappointing, we do understand and accept the requirement of the competing nations to place the world cup at the forefront of their planning."
