Antenatal diagnosis of placenta accreta spectrum (PAS) disorders.

Antenatal diagnosis of placenta accreta spectrum (PAS) disorders allows planned management by a multidisciplinary team in a tertiary center, and thus can reduce hemorrhagic morbidity, compared with intrapartum diagnosis. Previous Cesarean section and placenta previa are the two most common risk factors. Prenatal ultrasound is a promising diagnostic tool for PAS in the second or third trimester. Recent evidence shows sonographic markers of PAS can be present in the first trimester. Prenatal ultrasound may help predict the depth and topography of placental invasion which are the major determinants of maternal morbidity. The presence of increased vascularity in the inferior part of the lower uterine segment and the parametrial region is associated with a more severe disorder according to a newly proposed staging system. In this chapter, we will discuss how to improve the prediction of PAS, the depth, and topography of placental invasion.