I too am very sorry to hear about your miscarriage. My DW almost lost our first DD and it was a very anxious time. Fortunately, her ob/gyn had her come to his office immediately for a blood test. We found out she was deficient in a certain hormone (progesterone?), was able to provide hormone supplements and saved the baby just in time. Apparently, w/o this hormone the fetal sac pulls away from the uterine wall causing bleeding and the miscarriage. Sure enough she had the same problem with the second DD, but the doctor and DW was already prepared for it.
Several friends of ours had lost pregnancies before their ob/gyn figured out it was the same problem my wife had. I bring this up in case others here have had similar pregnancy problems as well. Apparently not all doctors rush to do blood tests until it's too late. Some even think this is just part of nature and don't want to do anything about it. BTW, my wife's ob/gyn happened to be certified for dealing with high-risk pregnancies as well (although we didn't come to him because of this). So maybe he had seen enough of these in the past to know what to do quickly for my wife.
I'm not saying this is the cause for anyone's miscarriage, but maybe this info will be of some help to some one.