Transfer to the Fetus cont'd - doe-std-1128-98

DOE-STD-1128-98

following prenatal or neonatal exposure gradually moves into the bone

matrix during subsequent bone-remodeling processes.

The radiation doses produced in the embryonic stage are assumed to be

relatively homogeneous and represent a small fraction of the doses

received by the pregnant woman when averaged over all tissues. The dose

to the fetus would constitute an even smaller fraction of the maternal dose

to any tissue in which there was specific deposition (Sikov et al., 1992). As

gestation progresses, there is an increase in the relative plutonium

concentration in specific fetal tissues, namely the bone and liver (Sikov et

al., 1992). Although limited information is available, experimental animal

and human data suggest that the average concentration is higher in the fetus

during the second or third trimesters than in soft tissues of the pregnant

woman, exclusive of the liver, yet significantly less than in maternal tissues

of primary deposition, i.e., the bone and liver.

Because placental structures, including the yolk sac, effectively trap

plutonium, progenitor cells of the gametes and hematopoietic lines that

appear initially in the blood islands of the yolk sac are irradiated while they

are primitive stem cells. However, the dose received by the early

embryonic cells and the detriment produced is not currently known.

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