Comparative study of transperineal and transabdominal sonography in the diagnosis of placenta previa

Abstract

To assess the role of transperineal sonography (TPS) in the diagnosis of placenta previa in the third trimester and to compare it with transabdominal sonography (TAS). Seventy-five suspected cases of placenta previa were subjected to TAS with half full bladder and to the TPS with empty bladder to visualize the inner surface of the cervix and inferior edge of the placenta. The presence or absence of placenta previa was confirmed at delivery. TAS depicted the inferior edge of placenta in 98.7% of cases compared to 96% with TPS. Internal cervical os was visualized in 98.7% with TAS compared to 100% with TPS. Placenta previa was confirmed at delivery in 74 cases with one false positive in TPS, six false positive in TAS. The positive predictive value (PPV) value in the diagnosis of placenta previa was 92% with TAS compared to 98.6% with TPS. Accuracy of TPS in diagnosing placenta previa was 98.7%. PPV in the diagnosis of minor degree placenta previa was less 86.36% with TAS compared to TPS 100% though for major degree both are in agreement. TPS is a valuable procedure to compliment TAS in the diagnosis of placenta previa and helps to exclude false positive and to determine the mode of delivery, although it cannot replace TAS.