The word "hemorrhage" refers to an abnormally heavy blood flow. Although a typical miscarriage may involve vaginal bleeding that is heavier than a typical menstrual period, bleeding that is heavy enough to soak through a menstrual pad in under an hour may be a sign of hemorrhage and should be evaluated by a medical practitioner.
If you are concerned that your bleeding is too heavy, or if you have a loved one experiencing a miscarriage and you are concerned that she is showing signs of excessive blood loss, seek medical attention right away.
Bleeding and Spotting from the Vagina During Pregnancy. March of Dimes. Accessed Feb 27, 2010. http://www.marchofdimes.com/pnhec/188_25620.asp.