Various types of placenta accreta
Invasion of the placenta into the uterine wall is referred to as placenta accreta. Risk factors for placenta accreta include prior placenta previa, prior uterine surgery (cesarean section, myomectomy), prior retained products of conception, and multiparity. Placenta accreta is further defined as accreta vera (also called accreta; the most common type) if the placenta is only adherent to the uterine myometrium, increta if the placenta invades into the myometrium, and percreta if the placenta completely penetrates the myometrium (usually then extending up to/into the bladder). All forms of placenta accreta can be difficult to diagnose sonographically, but suggestive US features include absence of the normal subplacental hypoechoic zone, heterogeneous placental echotexture, subplacental vascular spaces, and placental extension into the bladder wall. The major complication of placenta accreta is massive maternal hemorrhage at delivery.
