I had warning with both my girls, so it was a HUGE shock to the system when I had none at all with DS.
No extra mucous, nothing! Trust me, I was looking!!
I did have 2 contractions the morning before, but still felt pretty normal with nohing else for the rest of that day.
Oh, the 5 hour start to finish labour was just as much of a shock! My last was 30 hours with about 15 - 20 hours of pre labour & white gluggy CM.
DD1 had a show for 2 days before.