Diagnosis of Placenta Praevia by Photoscanning With Albumin Labeled With Technetium Tc 99m

Abstract

The occurrence of vaginal bleeding during the third trimester of pregnancy presents a challenging problem in obstetrical diagnosis and management. If placenta praevia is the cause of bleeding, close medical observation is necessary and the majority of patients will be delivered by cesarean section prior to term. If placenta praevia is present, vaginal examination may cause sufficient hemorrhage that immediate delivery of the infant is necessary. A method for the accurate diagnosis of placenta praevia, without vaginal examination, when vaginal bleeding first occurs, therefore would be of great importance. Procedures to estimate the size and position of the placenta such as soft-tissue radiography, injection of radiopaque dye into the vascular bed of the placenta, or surface counting of the trace amounts of radioisotopes (usually iodinated I 131 serum albumin or sodium chromate Cr 51-tagged red blood cells) in the placental blood pool are clinically useful. Too often, however, these procedures