With DS, my water broke prior to the onset of labor.
I was halfway through my 3-mile walk when I felt a sharp pain in my upper thigh, so much that I considered asking a man washing his car if I could borrow his phone to call DH to pick me up. It went away, though; I finished my walk. Six hours later, in the car, I felt a trickle and thought I'd lost bladder control. Then I felt a gush and was sitting in a couple of inches of water by the time we got home.