small subchorionic hemorrhage?

What Causes a Subchorionic Hematoma? The specific causes of subchorionic hematoma aren't clear. There are some risk factors associated with them, including:  Malformation of the uterus History of recurrent miscarriages History of pelvic infections Trauma Early-onset preeclampsia, which is a serious pregnancy complication marked by high blood pressure and organ failure Severe high blood pressure In vitro fertilization 

This is a type of bleeding that occurs between your amniotic membrane, which is the membrane that surrounds your baby, and your uterine wall. It occurs when the placenta partially detaches from where it was implanted in the wall of your uterus. Subchorionic hematomas can be small or large. Small ones are more common.