Placenta accreta: prospective sonographic diagnosis in patients with placenta previa and prior cesarean section.

A prospective evaluation for possible placenta accreta was performed in 34 patients with placenta previa and a history of one or more cesarean sections. Sonographic criteria used included (1) loss of the normal hypoechoic retroplacental myometrial zone, (2) thinning or disruption of the hyperechoic uterine serosa-bladder interface, and (3) presence of focal exophytic masses. Of 18 patients with positive sonographic results, 14 had proof of placenta accreta and 16 of the patients underwent hysterectomy. Of 16 patients with negative sonographic results, only one had placenta accreta, and two patients required hysterectomy. Presence of numerous intraplacental vascular lacunae appears to be an additional risk criterion for placenta accreta, separate from the other criteria listed above.