I wondered about this as well. I had a miscarriage last wednesday. When I first started bleeding, I did a pregnancy test to see if it showed I was still pregnant. I had theee positive tests, 1 clearblue, 1 reveal and 1 first response, so with those and my symptoms, I was defnitely pregnant. On the day I bled, (just a very light bleed at first) the test showed negative, which sent me into blind panic and i went to see the midwife. by the the bleeding was heavier and I knew for sure I was losing it.