Thanks for the query.
Dark colored blood usually indicates collected blood in the endometrial cavity.
And just by the color we cannot confirm the miscarriage
The bleeding could be due to hormonal
So you once consult gynecologist, get examined and go for ultrasound
By this the possible cause for your repeated bleeding can be identified and treatment can be given accordingly.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429