Subchorionic hemorrhage occurs when there is perigestational hemorrhage and blood collects between the uterine wall and the chorionic membrane in pregnancy. It is a frequent cause of first and second trimester bleeding.

General imaging differential considerations include:

• retroplacental hemorrhage
• marginal subchorionic hematoma can mimic a twin gestational sac (particularly failed early twin gestational sac)
• chorioamniotic separation