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Placental venous lakes

Placental venous lakes refer to a phenomenon of formation of sonolucent cystic spaces centrally within the placenta. Finding placental lakes during a second trimester ultrasound scan is not associated with any utero-placental 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 peri-villous fibrin deposition with cystic change within areas of sub-chorionic fibrin.


Their presence tends to be associated with:


Radiographic features

Antenatal ultrasound

They are typically seen as relatively well defined hypo-echoic regions within the placenta. 

Colour Doppler imaging may show low-velocity laminar flow within.

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