Transfer of radiobismuth to the fetus in guinea-pigs

A small animal study was carried out in guinea-pigs to measure uptake of radiobismuth (207BiCl3) in fetal organs after intravenous administration to the mother. In this study, little activity was found to cross the placental barrier with <1% of the injected activity found in fetoplacental units of either the 1st or 3rd three week period of a 9 week full-term pregnancy. The majority of the activity in the fetoplacental unit was found in the placenta and amniotic sac. These preliminary results indicate that radiobismuth and hence the majority of activity present from the inhalation of short-lived radon decay products would be poorly transferred across the placenta. The poor placental transfer of the dominant radionuclide 214Bi across the placenta, is considered to result in a negligible dose from radon short-lived daughters to fetal organs. (author)