[Placental transfer of cadmium in pregnant women].

To clarify the maternal-fetal transfer of cadmium across the placenta, cadmium was determined in 21 paired samples of maternal blood, placenta and umbilical cord blood obtained at delivery from pregnant women who did not smoke and had no particular exposure to cadmium compounds in their history. Cadmium was detected in all the samples. In both maternal blood and umbilical cord blood, the cadmium concentrations in the red blood cells were remarkably higher than those in the plasma. The cadmium concentration in the umbilical cord blood was significantly lower than that in the maternal blood, suggesting that the placenta might effectively block the transfer of cadmium to fetuses in pregnant women. The placental cadmium concentration was the highest in the samples determined. The ratios of placental to maternal blood cadmium concentration were very large, indicating that cadmium preferentially accumulates in the placental tissues. On the other hand, the ratios of umbilical cord blood to placental cadmium concentration were very small, indicating that the placenta constitutes an effective barrier against cadmium; that is, the placental cadmium is hard to transfer to fetuses in pregnant women. The significantly positive correlations between maternal blood and placenta, between placenta and umbilical cord blood and between maternal blood and umbilical cord blood in terms of the concentrations of cadmium suggest that the amount of cadmium accumulated in placenta and transferred from mother to fetus is strongly influenced by the cadmium body burden of the mother.