What is the management of a subchorionic hematoma detected on obstetrics (OBS) ultrasound (US)?

Management of Subchorionic Hematoma on Obstetric Ultrasound

For small first-trimester subchorionic hematomas with documented fetal cardiac activity, expectant management with serial ultrasound monitoring is appropriate, while large hematomas or those in the second/third trimester require closer surveillance including umbilical artery Doppler studies and antenatal testing. 1, 2

Initial Diagnostic Assessment

When a subchorionic hematoma (SCH) is identified on ultrasound, document the following key features:

• Location relative to the placenta using transvaginal ultrasound as the primary imaging modality 1
• Presence of fetal cardiac activity using M-mode ultrasound or video clips (avoid pulsed Doppler in first trimester due to potential bioeffects on the developing embryo) 1
• Size of the hematoma both in absolute measurements and relative to gestational sac size 3
• Obtain quantitative beta-hCG level and complete blood count to assess for anemia and trend hormone levels 1
• Blood type and screen if not already on file, particularly to identify Rh-negative patients 1

First Trimester Management

Small Hematomas with Positive Cardiac Activity

• Prognosis is favorable when fetal cardiac activity is present 1
• Serial ultrasound examinations at 7-day intervals until bleeding ceases, hematoma disappears, or pregnancy outcome is determined 4, 5
• Consider bed rest during the duration of vaginal bleeding, as retrospective data suggests fewer spontaneous abortions (9.9% vs 23.3%) and higher term pregnancy rates (89% vs 70%) in women who adhered to bed rest compared to those who continued usual activities 5

Rh-Negative Patients

• Administer anti-D immunoglobulin (50 μg) to all Rh-negative patients with vaginal bleeding to prevent alloimmunization 1

Second and Third Trimester Management

SCH in later pregnancy carries higher risk and requires more intensive monitoring:

• Umbilical artery Doppler studies should be performed as part of comprehensive monitoring 4, 2
• Serial growth ultrasounds to monitor for fetal growth restriction, which is associated with second/third trimester SCH 2
• Antenatal fetal testing should be considered, particularly if the SCH is large or requires maternal blood transfusion 2
• Monitor for signs of hemodynamic instability in large SCH requiring hospitalization, with consideration of blood transfusion if significant blood loss occurs 4

Special Population: Anticoagulated Patients

If SCH is detected in a woman on anticoagulation:

• Immediately discontinue DOACs and switch to low molecular weight heparin 4
• Early obstetric review and enhanced fetal monitoring including assessment for subchorionic/retroplacental bleeding 6, 4
• Detailed first trimester scan (11-13+6 weeks) and anomaly scan (18-23 weeks) performed by experienced sonologist 6
• For DOAC exposure beyond first trimester, additional ultrasounds to monitor for fetal growth, well-being, and intracranial bleeding 6

Prognostic Factors

Poor prognostic indicators include:

• Large hematoma size (both relative and absolute) correlates with unfavorable outcomes 3
• Severity of vaginal bleeding is associated with worse prognosis 3
• Increasing hematoma size on follow-up examination predicts poor outcome 3
• Presence of maternal pain correlates with adverse outcomes 3

Common Pitfalls to Avoid

• Do not use pulsed Doppler ultrasound in first trimester for cardiac activity assessment; use M-mode instead to avoid potential bioeffects 1
• Do not confuse early first trimester SCH with normal decidual bleeding or other placental abnormalities like subamniotic hematomas 1
• Do not assume SCH is benign in second/third trimester—these cases are associated with preterm birth, preterm prelabor rupture of membranes, fetal growth restriction, and fetal demise 2
• Do not overlook Rh status—failure to administer anti-D immunoglobulin can lead to alloimmunization 1