Placental Transfer of F18 in Sheep

Abstract

Two pregnant ewes were operated utilizing a technique which allows access to the fetal circulation with the lamb in utero. F18 was injected intravenously into the ewe and the maternal and fetal blood levels of F18 were observed over a 2 hour period. These data were consistent with previous studies. In addition, total F18 recovery from the lambs was determined. Only 0.16% and 0.42% of the maternal dose was recovered in the respective experiments. These findings indicate that previously observed low fetal F18 blood levels were the result of limited placental transfer rather than rapid fetal plasma clearance of the tracer.