Fetal pericardial effusion

A fetal pericardial effusion (FPE) refers to an accumulation of pericardial fluid in utero. In order to be considered as abnormal, is it generally accepted that the pericardial fluid thickness should be greater than 2 mm.

Epidemiology

The estimated incidence is at ~ 2% of pregnancies ⁸.

Pathology

Associations

• a fetal percardial effusion can occur as a component of hydrops fetalis : where it is usually one of the earliest findings in hydrops ⁹
• fetal arrhythmia(s)
  • fetal tachyarrhythmia(s)
• congenital cardiac anomalies : especially if large ⁵
• fetal cardiac tumours : e.g. fetal pericardial teratoma
• increased incidence of chromosomal anomalies ^3,5
  • trisomy 21 ³

Radiographic assessment

Antenatal ultrasound

A fetal pericardial effsion is typically seen as anechoic fluid component greater than 2 mm surrounding the heart (similar to adults). There is no colour flow with Doppler interrogation (c.f. congential cardiac diverticulum ⁶). If the volume is relatively small, it may present as a lenticular or ovoid collection whereas larger pericardial effusion may give a heart beating in a "bag of water" type appearence.

Significance

A careful search for other associations (inclusive of features of hydrops) is recommended.

In the absence of other sonographic abnormalities, an isolated fetal pericardial fluid collection up to 7 mm in thickness is not thought to be associated with an adverse outcome ¹.

Differential diagnosis

For a small atypical effusion consider

• congenital cardiac diverticulum : demonstrates colour flow within

See also

• pericardial effusion