Subchorionic hematoma (SCH) describes blood collection between the chorionic membrane and uterine wall (decidua), the most common ultrasonographic abnormality of early pregnancy. It is detected in 1.7-3.1% of first-trimester pregnancies, rising to 18-22% in pregnancies presenting with vaginal bleeding. Pathogenesis involves trophoblastic invasion eroding decidual vessels or bleeding from the implantation site. Most SCH show spontaneous resolution; however, large hematomas (>50% of gestational sac area) increase the risk of miscarriage, preterm delivery, and abruption. On ultrasound, a crescent-shaped collection is seen between the chorionic membrane and endometrium — echogenicity varies with hematoma age: acute hyperechoic, subacute hypoechoic, chronic anechoic.
Age Range
18-45
Peak Age
28
Gender
Female predominant
Prevalence
Common
Subchorionic hematoma forms from disruption of decidual vessels during or after implantation of chorionic villi into the decidual layer. During early pregnancy, trophoblastic invasion of spiral arteries inevitably causes local vascular damage — normally these small hemorrhages are controlled by hemostatic mechanisms. However, with excessive invasion, inadequate coagulation, or decidual damage (endometritis, curettage history), bleeding cannot be controlled → hematoma accumulates between the chorionic membrane and decidua. The hematoma lifts the chorionic membrane creating a crescent-shaped collection. In small hematomas (<20% of gestational sac area), trophoblastic function is preserved and the hematoma resolves within weeks. In large hematomas, extensive chorionic membrane separation from the decidual layer impairs trophoblastic perfusion → embryonic nutrition decreases → miscarriage risk increases. US echogenicity changes with time: fresh blood is hyperechoic (dense packing of erythrocytes and fibrin network → many acoustic interfaces), lysed blood is hypoechoic-anechoic (cellular components break down → acoustic interfaces decrease). This time-echogenicity relationship helps estimate hematoma age.
Crescent-shaped collection of variable echogenicity between the chorionic membrane and uterine wall adjacent to the gestational sac — pathognomonic ultrasonographic finding of subchorionic hematoma. Echogenicity depends on hematoma age and prognostic size assessment guides management decisions.
A crescent/crescentic collection is seen between the chorionic membrane and uterine wall adjacent to the gestational sac. It appears hyperechoic in acute phase, hypoechoic in subacute phase, and anechoic in chronic phase. The collection partially surrounds the gestational sac and pushes the chorionic membrane inward. Size measurement is taken at the largest dimension and compared to gestational sac area. Collection borders may be smooth or irregular — irregular borders suggest organized hematoma or active bleeding.
Report Sentence
A crescent-shaped collection is seen adjacent to the gestational sac, consistent with subchorionic hematoma.
Elevation of the chorionic membrane by the hematoma is seen — the membrane separates from the gestational sac and folds inward. The degree of membrane elevation correlates with hematoma size. The thin, smooth chorionic membrane is clearly visualized with collection localized behind it. This finding helps differentiate subchorionic from subamniotic hematoma. On real-time US, membrane undulation with fetal movements can be observed.
Report Sentence
Elevation of the chorionic membrane by the hematoma is noted.
Hematoma size is measured in three dimensions (length x width x depth) and compared to gestational sac area. Small hematoma (<20% of gestational sac area): good prognosis, >95% live birth. Medium hematoma (20-50%): moderate risk, close follow-up needed. Large hematoma (>50%): high miscarriage risk (40-65%). Hematoma localization is also important — hematomas at the placental margin (retroplacental) carry higher risk than central ones because they directly impair placental perfusion.
Report Sentence
Subchorionic hematoma measures __ x __ x __ mm, occupying approximately __% of the gestational sac area.
No vascularity is seen within the hematoma area on color Doppler (avascular collection), but trophoblastic flow around the gestational sac is preserved. This finding confirms the hematoma is not a vascular structure and helps investigate active bleeding focus. Rarely, an active bleeding point (arterial jet) may be detected at the hematoma edge — this indicates ongoing active bleeding and is a poor prognostic sign.
Report Sentence
The hematoma is avascular on color Doppler with preserved surrounding trophoblastic flow.
Follow-up US demonstrates progressive shrinkage or complete resolution of the hematoma. Small hematomas typically resolve within 2-4 weeks. Echogenicity change is also followed — hyperechoic hematoma transitions to hypoechoic/anechoic phase then disappears. Hematoma enlargement or new bleeding areas is a poor prognostic sign. Preservation of embryonic heartbeat indicates good prognosis.
Report Sentence
Decrease in subchorionic hematoma size is noted on follow-up US, consistent with resolution.
On T1-weighted MRI, subchorionic hematoma signal intensity varies with hematoma age: acute deoxyhemoglobin (T1 isointense), early subacute methemoglobin (T1 hyperintense — bright), late subacute (T1 hyperintense), chronic hemosiderin (T1 hypointense). MRI provides additional information to US especially in determining hematoma age and in complicated cases (suspected abruption, retroplacental hematoma).
Report Sentence
Subchorionic hyperintense area on T1-weighted MRI is consistent with subacute hematoma.
Criteria
Hematoma less than 20% of gestational sac area
Distinct Features
Good prognosis, >95% live birth, most resolve spontaneously within 2-4 weeks, conservative follow-up sufficient, no activity restriction needed
Criteria
Hematoma greater than 50% of gestational sac area
Distinct Features
High miscarriage risk (40-65%), increased abruption risk, requires close follow-up, bed rest recommended, progesterone support considered, weekly US follow-up mandatory
Criteria
Hematoma localized behind the placenta, between placenta and myometrium
Distinct Features
Higher risk than other locations, highest risk of progression to abruption, placental function may be impaired, fetal heart rate and growth monitoring required
Distinguishing Feature
Abruption shows painful bleeding with retroplacental hematoma (between placenta and myometrium) and typically occurs in late pregnancy; SCH is usually painless or mild bleeding with subchorionic collection (between chorionic membrane and decidua) detected in early pregnancy
Distinguishing Feature
Complete molar pregnancy shows 'snowstorm' pattern without fetal parts and β-hCG is very high; SCH has normal gestational sac, normal embryo, and homogeneous placenta
Distinguishing Feature
Ectopic pregnancy shows empty uterus with adnexal mass/ring sign; SCH has normal intrauterine pregnancy with subchorionic collection adjacent to the sac
Urgency
routineManagement
conservativeBiopsy
Not NeededFollow-up
3-monthSmall SCH are usually managed conservatively with good prognosis. Follow-up US at 2-3 week intervals is recommended. Large hematomas (>50%) require close clinical follow-up, activity restriction, and vaginal bleeding monitoring. Hematoma enlargement or loss of embryonic heartbeat are poor prognostic signs. Anti-D immunoglobulin should be administered to Rh-negative patients. Progesterone support is used in some centers for large/persistent hematomas but evidence level is limited. Retroplacental hematomas require obstetric consultation due to abruption risk.
Most subchorionic hematomas resolve spontaneously with good prognosis. Risk is assessed by comparing hematoma size to gestational sac size. Large hematomas (>50% area), those detected in early gestational age, and retroplacental locations carry higher complication risk. Serial US follow-up is recommended.