What is a subchorionic hemorrhage?

Subchorionic Hemorrhage: Definition and Clinical Implications

A subchorionic hemorrhage (SCH) is a collection of blood between the chorion membrane and the uterine wall, representing separation of the placental membranes from the decidua basalis of the uterus. This condition is typically detected on ultrasound examination during pregnancy and can vary significantly in size and clinical significance.

Characteristics and Diagnosis

• SCH is primarily diagnosed through ultrasound imaging, appearing as a hypoechoic or anechoic collection between the chorion and uterine wall 1
• Incidence varies widely in studies, ranging from 4% to 48% of pregnancies 2
• Most commonly detected in the first trimester, though can occur in second and third trimesters as well 1
• SCH can be classified by size:
  • Small: Limited separation with minimal blood collection
  • Medium: Moderate separation with noticeable blood collection
  • Large: Extensive separation with significant blood accumulation 3

Risk Factors

• Maternal coagulation disorders, particularly factor deficiencies
• Anticoagulation therapy during pregnancy
• No other consistent risk factors have been definitively established 1

Clinical Presentation

• First trimester vaginal bleeding is the most common presenting symptom
• The severity of symptoms often correlates with the size of the hemorrhage
• Some SCHs are asymptomatic and discovered incidentally on routine ultrasound
• Larger SCHs are more likely to cause noticeable symptoms 3

Pregnancy Outcomes and Complications

The clinical significance of SCH varies based on:

1. Size of hemorrhage: Larger SCHs (especially those requiring blood transfusion) carry greater risks 3
2. Gestational age at detection: Second and third trimester SCHs generally pose higher risks than first trimester SCHs 1
3. Location of the hemorrhage: Pre-placental and subchorionic locations may have different implications 4

Associated complications include:

• First trimester:

  • Increased risk of early pregnancy loss 3
  • Lower gestational age at delivery 3

• Second/third trimesters:

  • Placental abruption (3.6% vs 0.6% in pregnancies without SCH) 5
  • Preterm delivery (15.5% vs 10.5% in pregnancies without SCH) 5
  • Preterm premature rupture of membranes 1
  • Intrauterine growth restriction 3
  • Intrauterine fetal demise (in severe cases) 1

Management Considerations

• No proven specific treatment exists for SCH 1
• Management is primarily expectant with close monitoring
• For larger SCHs, consider:
  • Serial ultrasound examinations to monitor size and resolution
  • Fetal growth assessments
  • Umbilical artery Doppler studies
  • Antenatal fetal testing, particularly for large SCHs or those requiring maternal blood transfusion 1

Prognosis

• Small SCHs in the first trimester typically resolve spontaneously and often have good outcomes
• Medium to large SCHs, especially those detected in later pregnancy, warrant closer surveillance due to increased risks of adverse outcomes
• The prognosis worsens with increasing size of the hemorrhage, with large SCHs (SCH-III) showing significantly higher rates of complications including early pregnancy loss, IUGR, placental abruption, and preterm delivery 3

While many SCHs resolve without intervention, the condition should be taken seriously, particularly when large or detected in later pregnancy, as it can be associated with significant maternal and fetal complications.