How do you tell the difference between a heavy period and an early miscarriage?

Pregnancy test: At the time your period is due, you would have a positive pregnancy test if you have conceived. If your period is due and you have a negative pregnancy test - you are probably menstruating rather than miscarrying.

Difficult: Alot of miscarriages occur at the same time as a period, resulting in a heavy period, but not all heavy periods are due to miscarriages. The only way you could really tell at this point would be to do a blood test to test for betahcg and follow the levels to tell if you actually were pregnant.