·         Succenturiate lobe- One or more accessory lobes attached to the main placental vessels. The accessory lobe may be in previa position with its associated complications. Accessory lobes may also be retained after delivery.

·         Placental lakes- Large placental lakes lie in the intervillous spaces and contain moving blood.

·         Highly echogenic areas- Normal appearance in an aging placenta.

·         Placental cysts- Most cyst-like areas in the placenta are related to blood vessels. However, nonvascular placental cysts are not uncommon.

·         Placenta accreta - Normally there is villous invasion of the decidua. Occasionally the chorionic villi penetrate deeply into the myometrium. Placenta accreta increases the likelihood of placental retention, persistent bleeding or infections post delivery. The sonolucent area seen in the retroplacental region is lost in the accreta variety.

·         Placenta increta (17%)- The villi extend through the myomentrium.

·         Placenta percreta (5%)- the villi penetrate the uterine serosa.

·         Circumvallate placenta- The fetal membranes are attached to the inner aspect of the placenta instead of its edges. A depression is often seen at the point of membrane insertion, giving the appearance of a ‘ditch’.

·         Batteldore placenta- The umbilical cord inserts into the edge of the placenta and not in the centre. Rarely the cord in enter the membranes, with the vessels running through the membranes to reach the placenta.

·         Systemic maternal disorders- The placenta may be thickened Rh incompatibility, gestational diabetes and mild cases of nongestational diabetes. Systemic maternal infections (e.g. syphilis and maternal anemia may also cause thickening. There is a than normal incidence of placental infarction and abruption in emia of pregnancy.

·         Placenta previa-  Sonographic diagnosis depends upon the identification of placental tissue covering part or all the internal os. Placenta previa is associated with: (1) increasing maternal age; (2) multiparity; (3) uterine surgery.

Classification of placental location

 

Grade 1 Low lying

 

Grade 2 Marginal previa

 

Grade 3 Partial previa (complete asymmetrical)

Grade 4 Complete previa (complete symmetrical).