A subchorionic hematoma is a bleed/blood clot during pregnancy. It is the build up of blood between the uterine lining and the chorion (the outer fetal membrane, next to the uterus) or under the placenta itself. You may or may not experience spotting but for others it can be very heavy bleeding. Sometimes the bleed eventually will bleed out but in some cases it can be scary. Bleeding in pregnancy can be hard and scary but sometimes normal, talk with your provider if you experience bleeding and see what is going on.