We sought (1) to describe an anatomic defect of the uterine cavity in the anterior isthmus diagnosed by transvaginal sonography in a group of premenopausal women with previous cesarean deliveries, (2) to establish whether there is an association between the presence of the pouch and a bleeding disturbance, and (3) to compare the diagnostic efficacy of transvaginal sonography versus hysteroscopy for the detection of this defect.