Fetal toxicity of cadmium in the rat: Decreased utero-placental blood flow

Previous studies have shown that fetuses can tolerate direct injections of CdCl₂ in amounts greater than those which cross the placenta following maternal injections. Thus, fetal death is not the result of direct effects of cadmium on the fetus. Alterations in utero-placental blood flow were investigated as a possible mechanism of fetal toxicity. Organ blood flow was measured using the microsphere technique. Utero-placental blood flow was unchanged from control values 8–10 hr following 40 μmol/kg CdCl₂ on Day 18 but was reduced 40 and 73% from control values at 12–16 and 18–24 hr, respectively. Fetal death increased from 5 to 20 to 60% during the same time periods. Blood flow to maternal organs was unchanged from control values with the exception of the adrenal after 12–16 hr and myometrium at 18–24 hr. Histologic examination of placentae indicated that the placental necrosis, fetal death, and utero-placental blood flow alterations occurred over a similar time period. Thus, a decrease in placental blood flow was associated with placental necrosis and fetal death. However, it is not apparent whether placental necrosis was a cause or an effect of the decrease in utero-placental blood flow.