ITs hard to explain, but i just knew something wasnt right, i just had that "feeling" it wasnt going to end well, with my first mc, i had no idea, i had a hb then at 11 weeks it all went downhill, but with the 2nd one it was 6weeks 2days, so maybe my body knew cause it had been there before, i also had a dream a few days before that i was in labour and the baby didnt make it, the dreamwas quite physical as well, like i felt like i was pushing the baby out, if that made sence.
Sorry not much help in answering the actual question, but i think we have such a poweful intuition that sometime we just know.