Hence women who once lived in an lead-rich environment may pass on the toxin to their unborn offspring. The amount of lead present in the placenta indicates long-term exposure of the mother to the metal. It is usually stored in the skeletal tissues. During pregnancy, for instance, calcium is removed from a woman's bones and enters the blood stream. It then passes through the placenta and helps strengthen the developing embryo's skeleton.
Recent studies say that lead travels from the bone to the blood stream in a fashion quite similar.
Lead from the mother's blood stream trables to the placental tissue during pregnancy. However, experts cannot determine the amount of lead that travels from the mothers blood stream to the placental tissues during this period. There is an interesting reasoning behind the placenta being chosen as the biological material for analysis. Apart from being the largest available biopsy tissue, it has the added advantage of assessing accumulation of toxic chemicals over the nine months of pregnancy. Moreover, the placental tissue is perennial and plentiful.