Comparison of transabdominal and transvaginal sonography in the diagnosis of placenta previa.

PURPOSE

To compare the accuracies of transabdominal sonography (TAS) and transvaginal sonography (TVS) in the diagnosis of placenta previa.

METHODS

A prospective, cross-sectional study was conducted at a university hospital. Both TAS and TVS were performed on 81 pregnant women with a suspicion of placenta previa in the third trimester. The final diagnosis was confirmed at delivery. The agreement between the two ultrasound methods and the parameters of each method were calculated.

RESULTS

Fifty-eight percent of the women had a placenta previa. The sensitivities of TAS and TVS were 86% (95% CI 78-94%) and 95% (95% CI 91-100%), respectively (p= 0.2). The specificity of both methods was 93% (95 CI 88-99%), and the overall accuracies of TAS and TVS were 89% (95% CI 82-96%) and 94% (95% CI 89-100%), respectively. When TAS was followed by TVS, 23% of the previous diagnoses were changed. The agreement between both methods was good (Kappa value = 0.7, 95%CI 0.55-0.86).

CONCLUSIONS

For the diagnosis of placenta previa, TAS showed a high sensitivity and specificity, which were comparable to those of TVS.