| Blood Lead Changes during Pregnancy and Postpartum with Calcium Supplementation Brian L. Gulson,1,2 Karen J. Mizon,1 Jacqueline M. Palmer,2 Michael J. Korsch,2 Alan J. Taylor,3 and Kathryn R. Mahaffey4 1Graduate School of the Environment, Macquarie University, Sydney, New South Wales, Australia; 2Commonwealth Scientific and Industrial Research Organisation/Division of Exploration and Mining, North Ryde, New South Wales, Australia; 3Department of Psychology, Macquarie University, Sydney, New South Wales, Australia; 4U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Washington, DC, USA Abstract
Pregnancy and lactation are times of physiologic stress during which bone turnover is accelerated. Previous studies have demonstrated that there is increased mobilization of lead from the maternal skeleton at this time and that calcium supplementation may have a protective effect. Ten immigrants to Australia were provided with either calcium carbonate or a complex calcium supplement (~ 1 g/day) during pregnancy and for 6 months postpartum. Two immigrant subjects who did not conceive acted as controls. Sampling involved monthly venous blood samples throughout pregnancy and every 2 months postpartum, and quarterly environmental samples and 6-day duplicate diets. The geometric mean blood lead at the time of first sampling was 2.4 µg/dL (range, 1.4-6.5) . Increases in blood lead during the third trimester, corrected for hematocrit, compared with the minimum value observed, varied from 10 to 50%, with a geometric mean of 25%. The increases generally occurred at 6-8 months gestation, in contrast with that found for a previous cohort, characterized by very low calcium intakes, where the increases occurred at 3-6 months. Large increases in blood lead concentration were found during the postpartum period compared with those during pregnancy ; blood lead concentrations increased by between 30 and 95% (geometric mean 65% ; n = 8) from the minimum value observed during late pregnancy. From late pregnancy through postpartum, there were significant increases in the lead isotopic ratios from the minimum value observed during late pregnancy for 3 of 8 subjects (p < 0.01) . The observed changes are considered to reflect increases in mobilization of lead from the skeleton despite calcium supplementation. The identical isotopic ratios in maternal and cord blood provide further confirmation of placental transfer of lead. The extra flux released from bone during late pregnancy and postpartum varies from 50 to 380 µg lead (geometric mean, 145 µg lead) compared with 330 µg lead in the previous cohort. For subjects replete in calcium, the delay in increase in blood lead and halving of the extra flux released from bone during late pregnancy and postpartum may provide less lead exposure to the developing fetus and newly born infant. Nevertheless, as shown in several other studies on calcium relationships with bone turnover, calcium supplementation appears to provide limited benefit for lead toxicity during lactation. Key words: blood, bone remodeling, calcium supplementation, lead, lead isotopes, postpartum, pregnancy. Environ Health Perspect 112:1499-1507 (2004) . doi:10.1289/ehp.6548 available via http://dx.doi.org/ [Online 27 July 2004]
Address correspondence to B.L. Gulson, Graduate School of the Environment, Macquarie University, Sydney, NSW 2109 Australia. Telephone: 61-2-9850-7983. Fax: 61-2-9850-7972. E-mail: bgulson@gse.mq.edu.au We thank M. Salter for phlebotomy, L. Munoz for technical assistance, the participants in this study, English Language Schools in Sydney, B. Jameson and B. Ragan of the National Institute of Environmental Health Sciences (NIEHS) and P. Mushak for their support and encouragement over many years, J. Fouts for reviewing an earlier version of the manuscript, and R. Setright of Blackmores for supply of one of the products. This research was largely funded by the NIEHS through NO1-ES0252. The authors declare they have no competing financial interests. Received 26 June 2003 ; accepted 27 July 2004.
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