<unk>  is the pooling of blood<unk>  between the chorion, a membrane surrounding the embryo, and the uterine wall. It occurs in about 3.1% of all pregnancies, it is the most common sonographic abnormality and the most common cause of first trimester bleeding.
Chorionic hematoma
Encephalocele
Subdural hygroma
Asteroid hyalosis
Exencephaly
Omphalocele
Anencephaly
Cystic hygroma