Placenta accreta. Additional sonographic observations.

Recent reports describe the antenatal sonographic diagnosis of placenta accreta based on failure to visualize a hypoechoic zone at the placental margin. This finding was confirmed in our series of seven cases. New observations in this series include prominent large or multiple placental venous lakes and periuterine vascularity in six of seven cases, and progressive thinning and disappearance of the retroplacental hypoechoic zone on sequential examinations in two of seven cases. Loss of normal venous flow pattern on Doppler interrogation of the peripheral placental margin also appeared to be of value in two patients. Histologic correlates for these findings are suggested on the basis of the primary histopathologic feature of placenta accreta: deficiency of the decidua basalis. Differential diagnostic considerations, including abdominal pregnancy and trophoblastic disease, also are discussed.