Chorionic hematoma

Chorionic hematoma
Other names	Chorionic hemorrhage, chorionic bleed
Ultrasound showing a subchorionic hemorrhage[1]

Chorionic hematoma is the pooling of blood (hematoma) between the chorion, a membrane surrounding the embryo, and the uterine wall.^[2] It occurs in about 3.1% of all pregnancies,^[2] it is the most common sonographic abnormality and the most common cause of first trimester bleeding.^[3]

Chorionic hematomas can be caused by the separation of the chorion from the endometrium (inner membrane of the uterus). Hematomas are classified by their location between tissue layers:^[4]

• Subchorionic hematomas, the most common type, are between the chorion and endometrium.
• Retroplacental hematomas are entirely behind the placenta and not touching the gestational sac.
• Subamniotic or preplacental hematomas are contained within amnion and chorion. Rare.

Most patients with a small subchorionic hematoma are asymptomatic.^[5] Symptoms include vaginal bleeding, abdominal pain, premature labor and threatened miscarriage.^[6]

Ultrasonography is the preferred method of diagnosis.^[7] A chorionic hematoma appears on ultrasound as a hypoechoic crescent adjacent to the gestational sac. The hematoma is considered small if it is under 20% of the size of the sac and large if it is over 50%.^[2]

The presence of subchorionic bleeding around the gestational sac does not have a significant association with miscarriage overall.^[8][9] However, the case of intrauterine hematoma observed before 9 weeks of gestational age has been associated with an increased risk of miscarriage.^[10] In one study women who complied with instructions for bed rest for the duration of bleeding had a lower rate of miscarriage and a higher rate of term pregnancy than non-compliant women. The study had several limitations; results were severely confounded by inherent differences between compliant and non-compliant women.^[11]

• Chorionic bump