Project Summary (2000-2006)

Recent evidence indicates that there is a marked increase in the mobilization of lead (Pb) from maternal bone stores into circulation during pregnancy and lactation. Data generated within the Harvard SBRP, as well as data from other sources, indicate that this phenomenon carries a significant risk of fetal toxicity in the form of growth (decreased birth weight, head circumference, birth length) and subsequent cognitive development. These findings pose a major public health problem, even among societies with declining lead exposure because pockets of high lead exposure persist (including some communities in proximity to hazardous waste) and lead in bone has a very long residence time (years to decades).

One possible strategy for suppressing the mobilization of maternal bone lead stores during pregnancy is nutritional intervention. To investigate the potential of this approach, researchers are recruiting a new sample of women in Mexico City who have relatively high bone lead levels. The women will participate in a randomized, double-blinded, placebo-controlled trial of supplements containing calcium. Maternal measurements will be taken to evaluate whether the supplements suppress bone resorption and the resulting mobilization of lead from bone into plasma during pregnancy, and into breast milk during the postpartum period. These measurements include bone lead, bone resorption (by assaying N-telopeptide of type I collagen in urine [urinary NTX]), whole blood lead, plasma lead and breast milk lead levels. Project investigators will measure maternal plasma and breast milk lead levels because these are the most direct sources of fetal and infant lead exposures, and recent research suggests that maternal venous blood lead levels do not adequately reflect either of these parameters. The results will help to evaluate the hypothesis that calcium supplements will significantly decrease urinary NTX, plasma lead, and breast milk lead levels. The relationship of plasma lead levels to birth anthropometry measures is also being investigated. This research may provide a means of preventing secondary toxicity from accumulated lead burdens among women of reproductive age.