First time, I just felt the usual birth pains, my waters broke near the end I think, I was in a bath at the time.

Second time, nothing, I was asleep. But I woke with a huge confused start, because I heard the pop and felt it quite strongly at the same time, even though I'd been asleep, I woke straight away knowing what had happened. It was a very sudden, definite feeling for me the second time around. But nothing before.