Placenta accreta
（重定向自Adherent placenta）
Placenta accreta occurs when all or part of the placenta attaches abnormally to the myometrium (the muscular layer of the uterine wall). Three grades of abnormal placental attachment are defined according to the depth of invasion:
Because of abnormal attachment to the myometrium, placenta accreta is associated with an increased risk of heavy bleeding at the time of attempted placental delivery. The need for transfusion of blood products is frequent, and hysterectomy is sometimes required to control life-threatening hemorrhage.