Transabdominal sonographic diagnosis of placenta praevia in a tertiary maternity unit in Jos, Nigeria: How accurate?

Abstract

Context: Ultrasonography has revolutionalise the diagnosis and  management of placenta praevia, a high risk pregnancy associated with life threatening maternal and fetal complications. Although transabdominal sonography (TAS) is a valuable obstetric imaging technique in this maternity unit, its value in the diagnosis of placenta praevia has not been assessed.
Objectives: To assess the accuracy and false positive rate of TAS in the diagnosis of placenta praevia and to determine the types of placenta praevia.
Study design, Settings and Subjects: A prospective descriptive study of all women with transabdominal sonographic diagnosis of placenta praevia in the maternity unit of Jos University Teaching Hospital, Jos, Nigeria between January 2006 and June 2009. All the patients had sonographic assessment with scanner Toshiba just vision 400, with a 3.5MHz curvilinear transducer. The presence or absence of placenta praevia was confirmed at caesarean
delivery.

Main outcome measures: Accuracy and false positive rate of TAS in the diagnosis of placenta praevia as well as it types.
Results: Placenta praevia was confirmed intra-operatively in 121 out of the 137 patients with ultrasound diagnosis. Thus, the diagnostic accuracy of TAS was 88.3% and a false positive rate of 11.7% with about 68.8% of the false positive cases having abruptio placentae. Seventy four (61.2%) and 47 (38.8%) were major and minor degree placenta praevia respectively.

Conclusion: TAS is a valuable and accurate modality for the diagnosis of placenta praevia in this maternity unit but more vigilance is needed during the procedure so as to reduce the false positive rate. The use of vaginal ultrasonography in this centre may significantly improve the accuracy in the diagnosis of the condition.

Keywords: Placenta praevia, Transabdominal, Sonography, accuracy, false positive rate.