Whats causes subchorionic hematomas to come and go in pregnancy? at 17w does it mean i have a blood clotting disorder? i would like to know how frequently obgyns tend to see it cause 17w + miscarriage/still birth or placenta abruption? is it rare?

Apruption ?'s: A subchorionic hemorrhage (SCH) occurs when a portion of the placenta separates from its attachment to the uterus. Insertion of the placenta near the cervical canal presents more likelihood of a SCH secondary to trauma (increased physical activity, etc). Placental attachment is very redundant, however, and adverse effects are modified with few ending in miscarriage, etc..