Subchorionic Cysts & Placental Villi: Understanding Placenta Formation

Question
what is subchorionic cysts? and, mature chorionic villi mean?

Answer
In he formation of the placenta, there can be cysts or blood clots that form within the layers of the placental membranes. One of the three membranes is called the chorion. Sometimes there is some vaginal bleeding from this area and it is called a "subchorionic bleed". It is self limiting and is of no consequence. Cysts that form within these layers are also usually harmless. The placenta has villi (finger like projections), that allow us to identify a pregnancy. If mature chorionic villi are seen it indicates that the fetus is close to term and that the placenta is a mature placenta.