What is a venous lake in a placenta?

Small collection of. Blood within placenta. It is usually contained and does not cause bleeding or issues for the fetus. Your doctor will probably follow the size and location of it and may refer you to an mfm specialist just to be safe.
Common finding. Unless associated with placenta previa, this is a common and insignificant sonographic finding. In the presence of previa, it is the hallmark of placenta accreta.