Lead and Pregnancy

The following article is a compilation of two articles. Most of the following is taken from an article called 'Danger Zones' printed in Macquarie University News, June 1997. The remainder is taken from an article 'Study finds lead link from mums to babies' from the Northern Herald, June 26, 1997. Reproduced with kind permission.

A joint Macquarie University CSIRO research project has discovered lead is transferred during pregnancy to the foetus and during breastfeeding to the child - possibly impairing intellectual development and contributing to child behavioural problems. Preliminary results from the study have also found women should substantially boost their daily intake of calcium during pregnancy and even more during breastfeeding to offset dissolution of lead-affected bone into the bloodstream to provide calcium and other sustenance to the developing child. One of the most important international studies of its kind, the research project - coordinated by the CSIRO and led by Macquarie University environmental scientist Professor Brian Gulson - has brought together the best researchers from Australian universities and medical research institutions. The multimillion dollar project is sponsored by the US National Institute of Environmental Health Sciences.

Professor Gulson said lead entered the environment from various industrial and commercial sources including leaded petrol but the most insidious unrecognised source was lead paint released during building renovation. More than 90% of lead accumulated in the body during pre-adult years is stored in the skeleton."We have now been able to show lead is definitely mobilised from the skeleton during pregnancy and perhaps even earlier than people thought," said Gulson.

During pregnancy and breast feeding calcium requirements became very high and if not provided in the diet, a mother’s bones partly dissolved to make up the calcium deficit. "Once lead is in the blood stream it goes across the placenta to the baby at a time of critical development of the central nervous system of the foetus.

"What we have shown is that it appears as though this could take place in the first three months and not just the last trimester of pregnancy as has previously been thought and that the baby’s brain is extremely immature at that stage and vulnerable to the toxic effects of lead.

"In a foetus there is no brain barrier to lead whereas in later life we have this barrier formed to protect the brain from toxins."

Professor Gulson said the study also found lead mobilised more in breast feeding than during pregnancy. "This is partly because there is a higher daily requirement of calcium during breast feeding than during pregnancy.

"The recommended daily intake of calcium for women is about 800mgs but should actually be as high as 1200 to 1300mgs during pregnancy and breast feeding." Professor Gulson said his team would now seek continued funding from US health agencies to study calcium supplementation with the aim of developing a quality intervention mechanism so dissolution of lead affected skeletal bone during pregnancy and breast feeding can be minimised. Preliminary follow-up research by the study team suggested women needed to have as much as 1300 milligrams of calcium every day to prevent their bones from dissolving and releasing the stored lead to their unborn baby.

Lead entering a woman’s bloodstream while pregnant would also be transferred directly to the foetus. Pregnant women were at the greatest risk when exposed to the lead of old paint in house renovations. Living near roads that carried 25,000 cars a day was also likely to affect a foetus. There were some preventative measures that could be taken, Professor Gulson said. "During the whole of your life, if you have a proper diet of things like calcium, iron, zinc and small amounts of copper, then that minimises the uptake of lead. The other thing, though, is that eating fatty foods appears to enhance the uptake of lead. "There are preventative measures you can take, right from the beginning."

Surprisingly the study showed the eastern European women, who had emigrated from highly polluted countries, had the same blood-lead levels or lower than their Australian counterparts. "I do not have specific evidence but I think it is tied up with the relatively small number of motor cars in their countries of origin.

"Overall the blood-lead levels in the trial group were not too high so, as leaded-petrol cars decrease, [in number] it will not be such a problem in developed countries. In developing areas where we are seeing an explosion in the number of leaded petrol vehicles it could quickly become a problem."

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