Placental venous lakes

Placental venous lakes refer to a phenomenon of formation of hypoechoic cystic spaces centrally within the placenta. Finding placental lakes during a second trimester ultrasound scan is not associated with any uteroplacental complication or with an adverse pregnancy outcome. They can, however, be abnormal if very diffuse or if seen very early in pregnancy.


Placental venous lakes are a common occurrence, reported to occur in approximately 20% of pregnancies.


They usually result from perivillous fibrin deposition with cystic change within areas of subchorionic fibrin.


Their presence tends to be associated with:


Radiographic features

Antenatal ultrasound
  • relatively well defined hypoechoic regions within the placenta
  • colour Doppler imaging may show low-velocity laminar flow within

Differential diagnosis

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