A safe and accurate method of localization of the placenta is still of prime importance in establishing a positive diagnosis of placenta previa. However, with the increasing use of amniocentesis1 for analysis of amniotic fluid and fetal transfusion in the management of erythroblastosis fetalis, for amniography, and for the diagnosis of fetal death and induction of labor in such cases by the instillation of hypertonic solutions, more specific knowledge of the exact location of the placenta becomes essential to eliminate the risk of trauma to the placenta when inserting the needle into the amniotic sac.
The use of radioactive isotopes for placental localization is generally accepted as superior to other techniques.2 Soft tissue x-ray techniques with or without contrast media3,4 have enjoyed a limited degree of success, being of little diagnostic value before the 35th week of gestation. Aortography5 and retrograde femoral arteriography6 are more
Krohn L, Jaffe HL, Adams R. Radioisotope Localization of the Placenta in Polaroid Color. JAMA. 1967;202(9):889–892. doi:10.1001/jama.1967.03130220077013