 Introduction/Background Placenta accreta spectrum disorder (PASD) is the current terminology recommended by the International Federation of Obstetrics and Gynecology (FIGO) and should replace terms such as abnormally adherent/invasive placenta or morbidly adherent placenta [1]. PASD refers to a variety of potential clinical complications, which may result from abnormal placental implantation. More specifically, placenta accreta refers to a defect in the decidua basalis in which the chorionic villi adhere directly to the myometrium with trophoblastic invasion. More invasive placentation includes placental increta, in which placental villi invade into the myometrium, and placenta percreta, in which the placenta villi invade through the myometrium and into the serosa and adjacent structures [2]. A single placenta can demonstrate varying degrees of invasiveness, and a decidual defect may be accompanied by focal loss of myometrium, often related to prior surgery or trauma. The pathology and underlying mechanism for placenta accreta is not well understood but is thought to be related to a defect in trophoblastic function versus a failure of normal decidualization or a combination of both [1,3,4]. The risk of severe and even life-threatening hemorrhage is greatest at the time of delivery when a portion of the placenta does not separate in the usual fashion. Accurate antenatal diagnosis is needed to plan for an appropriate delivery strategy at an experienced center in order to reduce maternal morbidity [11]. Management of delivery is variable; however, the American Congress of Obstetricians and Gynecologists (ACOG) and FIGO recommend planned cesarean delivery with or without hysterectomy depending on the suspected severity of PASD around 34 to 38 weeks. There is currently insufficient evidence to determine the exact optimal time of delivery.
Placenta Accreta Spectrum Disorder.  Introduction/Background Placenta accreta spectrum disorder (PASD) is the current terminology recommended by the International Federation of Obstetrics and Gynecology (FIGO) and should replace terms such as abnormally adherent/invasive placenta or morbidly adherent placenta [1]. PASD refers to a variety of potential clinical complications, which may result from abnormal placental implantation. More specifically, placenta accreta refers to a defect in the decidua basalis in which the chorionic villi adhere directly to the myometrium with trophoblastic invasion. More invasive placentation includes placental increta, in which placental villi invade into the myometrium, and placenta percreta, in which the placenta villi invade through the myometrium and into the serosa and adjacent structures [2]. A single placenta can demonstrate varying degrees of invasiveness, and a decidual defect may be accompanied by focal loss of myometrium, often related to prior surgery or trauma. The pathology and underlying mechanism for placenta accreta is not well understood but is thought to be related to a defect in trophoblastic function versus a failure of normal decidualization or a combination of both [1,3,4]. The risk of severe and even life-threatening hemorrhage is greatest at the time of delivery when a portion of the placenta does not separate in the usual fashion. Accurate antenatal diagnosis is needed to plan for an appropriate delivery strategy at an experienced center in order to reduce maternal morbidity [11]. Management of delivery is variable; however, the American Congress of Obstetricians and Gynecologists (ACOG) and FIGO recommend planned cesarean delivery with or without hysterectomy depending on the suspected severity of PASD around 34 to 38 weeks. There is currently insufficient evidence to determine the exact optimal time of delivery.