Placenta accreta spectrum (PAS) refers to a range of abnormal placental implantation where trophoblastic tissue invades beyond the normal decidual layer. Accreta describes superficial myometrial invasion; increta involves deeper myometrial invasion; percreta penetrates through the uterine serosa and may involve adjacent organs. PAS is strongly associated with prior uterine surgery and placenta previa. Ultrasound findings include loss of the clear space between the placenta and myometrium, placental lacunae (irregular vascular spaces), and bridging vessels crossing the uterine serosa.