|Other names: Chorionic hemorrhage, chorionic bleed|
|Ultrasound showing a subchorionic hemorrhage|
|Symptoms||None, vaginal bleeding, abdominal cramps|
|Complications||Pregnancy loss, preterm delivery, preterm rupture of membranes|
|Usual onset||10 to 20 wks gestational age|
|Risk factors||Miscarriage, uterine malformation, pelvic infections|
|Differential diagnosis||Ectopic pregnancy, twins, miscarriage, implantation bleeding, placental abruption, placenta previa, gestational trophoblastic disease|
|Treatment||Depends on symptoms and Rh status|
|Frequency||1 to 18% of pregnancies|
Chorionic hematoma is the pooling of blood between the chorion, a membrane surrounding the embryo, and the uterine wall. Symptoms may vary from none to vaginal bleeding. There is generally no pain, though some may have cramps. Large areas of bleeding are associated with pregnancy loss. Other complications may include preterm delivery and preterm rupture of membranes.
The cause is unclear. Risk factors include previous miscarriage, uterine malformation, and pelvic infections. The underlying mechanism is believed to involved detachment of the chorion from the uterus. Diagnosis is by ultrasound.
Signs and symptoms
Chorionic hematomas are due to a separation of the chorion from the endometrium (inner membrane of the uterus).
Ultrasonography is the preferred method of diagnosis. 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%.
Hematomas are classified by their location between tissue layers:
- 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.
Prognosis and treatment
The presence of subchorionic bleeding around the gestational sac is not association with miscarriage overall. However, the case of intrauterine hematoma observed before 9 weeks of gestational age has been associated with an increased risk of miscarriage. 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. 
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