“…Using Philips iU22 color US diagnostic system, with a probe frequency of 3.5 Hz, two US professional deputy chief physicians performed US images to assess whether there was placenta accreta, and the cases diagnosed with placenta accreta were classified according to the previous literature: In Grade I, the retroplacental space disappears and is occupied by placental tissue, the strong echo lines of the decidua disappear, and the myometrium becomes thin (<2 mm). In Grade II, in addition to the manifestations of Grade I, the myometrium disappears, and there are venous pools of different sizes in the placenta, which are the same as the abnormally dilated blood vessels on the uterine wall after the placenta [ 12 ]. In Grade III, in addition to grade II manifestations, the uterine serosa layer is interrupted, local blood vessels and solid mass shadows protrude to the bladder, the posterior wall of the bladder is not smooth or uneven, and at the same time, the authors classified cases where US failed to diagnose placenta accreta as Grade 0.…”