Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. 
Clinical Pharmacist and Master’s student in Clinical Pharmacy with research interests in pharmacovigilance, behavioral interventions in mental health, and AI applications in clinical decision support. Experience includes digital health research with Bloomsbury Health (London) and pharmacovigilance practice in patient support programs. Published work covers drug awareness among healthcare providers, postpartum depression management, and patient safety reporting. What was studied?
This study examined the mobilization of lead from maternal skeletal stores during pregnancy and lactation, and its transfer to the fetus. The researchers used a longitudinal cohort design with high-precision lead isotope fingerprinting, allowing them to distinguish between lead derived from long-term bone stores versus that from environmental exposure. The primary objective was to determine whether, when, and how much lead is mobilized from the maternal skeleton during pregnancy, and how this affects maternal and infant blood lead levels (PbB). By serially measuring blood and urine lead concentrations and isotopic compositions in pregnant women, their infants, and control groups, as well as systematically sampling environmental sources, the investigators provided a comprehensive view of endogenous versus exogenous lead exposure during gestation and early infancy. This research directly addresses concerns relevant to heavy metal certification programs, particularly regarding the endogenous release of toxic metals during physiological stressors such as pregnancy.
Who was studied?
The study population consisted mainly of European female immigrants of child-bearing age (18 to 35 years) who had recently relocated to urban Australia. These women were selected specifically because their bone lead isotopic signatures differed markedly from those of their new Australian environment, allowing clear differentiation of skeletal versus environmental lead. The initial cohort targeted 100 immigrants to yield at least 20 pregnant subjects, but at the interim analysis included 13 immigrant pregnancies (7 births) and 3 Australian control pregnancies (2 births). Nonpregnant immigrant women and second-generation Australian pregnant women served as control groups. Pregnant subjects also served as their own controls, with preconception, gestational, and postnatal lead measurements. Blood and urine samples were collected from mothers and infants, with extensive environmental monitoring (diet, house dust, water, urban air, gasoline) conducted throughout the study period. This careful cohort and control selection, with rigorous longitudinal sampling, provides a robust dataset for distinguishing sources and timing of lead exposure.
Most important findings
| Critical Points | Details |
|---|---|
| Skeletal Lead Mobilization | The study found a mean increase of 31% (±19%) in the skeletal contribution to maternal blood lead during pregnancy, with individual increases ranging from 9% to 65%. This mobilization was detectable even in women with low initial blood lead levels (mean PbB of 3.0 µg/dl). |
| Timing of Mobilization | Increases in blood lead and skeletal contribution were observed as early as the second month of gestation in some women, although most increases occurred in the latter half of pregnancy. This challenges previous assumptions that mobilization only occurs later in pregnancy. |
| Fetal Exposure | The ratio of cord to maternal blood lead varied from 0.54 to 1.05, but isotopic compositions were nearly identical, confirming significant placental transfer of mobilized skeletal lead to the fetus. |
| Environmental Contributions | Environmental lead intake (from diet, water, dust, air) was generally low and had minimal effect on maternal blood lead or its isotopic profile, confirming that the observed increases in PbB during pregnancy were due to endogenous skeletal release rather than new environmental exposures. |
| Control Comparisons | Nonpregnant immigrant controls and Australian pregnant controls showed negligible changes in blood lead or isotopic composition, supporting the conclusion that pregnancy-specific physiological changes drive the observed mobilization in immigrant subjects. |
| Public Health Relevance | Even after extended residence (>800 days) in the low-lead Australian environment, significant contributions of legacy skeletal lead remained detectable, highlighting the potential for internal stores to elevate maternal and fetal exposure long after environmental sources are reduced or eliminated. |
Key implications
The study demonstrates that pregnancy can significantly mobilize lead from long-term maternal bone stores, even at low background exposure, leading to increased maternal and fetal blood lead levels. For heavy metal certification, this underscores the necessity of accounting for endogenous sources when assessing risk in pregnant women and setting regulatory thresholds.
Citation
Gulson BL, Jameson CW, Mahaffey KR, Mizon KJ, Korsch MJ, Vimpani G. Pregnancy increases mobilization of lead from maternal skeleton. J Lab Clin Med. 1997;130(1):51-62.
Lead is a neurotoxic heavy metal with no safe exposure level. It contaminates food, consumer goods and drinking water, causing cognitive deficits, birth defects and cardiovascular disease. HMTC’s rigorous lead testing applies ALARA principles to protect infants and consumers and to prepare brands for tightening regulations.
