Keep an eye on her, if she isn't pushing yet, she may be in pre-labor. It can take many hours to only a few.
With pre-labor the kids are making their way to the birth canal. If all of a sudden, the kids drop off her sides when looking at her from behind and she isn't as big around anymore, Her flanks will be sunk in when she is getting close. Her tailhead will drop down and her ligs will be softened, to gone. Her udder may get really tight and shiny. Amber color clear tube like discharge, means she is really close.