Transfer and distribution of niobium-95 in adult, fetal, and newborn rats after injection during pregnancy.

Following i.v. injection of Nb-95 into pregnant rats, fetuses and newborns were dissected and measured for radioactivity after several time intervals. At any time only a small quantity of the administered radioactivity was transferred to fetus and newborn and the fetal tissue concentrations were always lower than the maternal ones. The highest ratio (0.6) between fetal and maternal tissue concentrations was found in bone.