Placenta previa--is the traditional diagnostic approach satisfactory?

The accuracy of the diagnosis of placenta previa using transvaginal sonography (TVS) was compared to that of the traditional transabdominal sonography (TAS). Seventy seven women were scanned by both methods and each sonographic diagnosis was compared to the placental location at delivery. TVS was superior to TAS in diagnosing placenta previa and invariably correct in ruling it out. TVS (and TAS) failed to predict the placental location at delivery only in women diagnosed as having marginal placenta previa prior to 35 weeks gestation. The use of the vaginal probe significantly improved the accuracy of the diagnosis of placenta previa.