Placenta Accreta Spectrum

Placenta accreta spectrum (PAS) is a complex obstetric disorder associated with a high rate of perinatal complications for both the pregnant patient and newborn, particularly when undiagnosed before delivery. It is a disorder that has risen in incidence over the past two decades, following an almost parallel rise in cesarean delivery (CD) rates. PAS is essentially the consequence of surgical damage to the uterine wall with loss of the normal decidual-myometrial interface, allowing the placenta to develop close to the large arteries of the uterine periphery. The transformation of these large vessels generates high-velocity flow inside the placenta, distorting the normal placental anatomy, as evidenced by the formation of “lacunae,” and is progressively associated with excessive fibrinoid deposition at the uteroplacental interface, making these two tissues inseparable, as though they are glued together. When first described more than 80 years ago, placenta accreta was identified at birth in patients with a history of prior manual removal of the placenta, uterine curettage, and/or after postpartum endometritis. Today, more than 95% of patients with PAS at birth present prenatally with a low-lying placenta or placenta previa with an anterior component and a history of prior lower-segment CDs. Patients with a high probability of PAS are best managed by a multidisciplinary team (MDT) with established expertise in complex pelvic surgery and full logistical support (immediate access to comprehensive blood products and to adult and neonatal intensive care) to optimize outcomes for both mother and newborn. The use of standardized PAS protocols is essential to improve prenatal screening, MDT management, and confirmation of the diagnosis after birth.