Maternal bone lead as an independent risk factor for fetal neurotoxicity: a prospective study.

OBJECTIVE A number of prospective studies have examined lead levels in umbilical cord blood at birth as predictors of infant mental development. Although several have found significant inverse associations, others have not. Measurement of lead levels in maternal bone, now recognized as the source of much fetal exposure, has the potential to serve as a better or complementary predictor of lead's effect on the fetus. Our objective was to compare lead levels in umbilical cord blood and maternal bone as independent predictors of infant mental development using a prospective design. METHODS We recruited women who were giving birth at 3 maternity hospitals in Mexico City that serve a homogeneous middle-class community. Umbilical cord blood lead levels were measured by graphite furnace atomic absorption spectroscopy, and maternal lead levels in cortical (tibial) and trabecular (patellar) bone were measured within 4 weeks of giving birth using a 109-Cd K-x-ray fluorescence instrument. At 24 months of age, each infant was assessed using the Bayley Scales of Infant Development-II (Spanish Version). RESULTS A total of 197 mother-infant pairs completed this portion of the study and had data on all variables of interest. After adjustment for other well-known determinants of infant neurodevelopment, including maternal age, IQ, and education; paternal education; marital status; breastfeeding duration; infant gender; and infant illness, lead levels in umbilical cord blood and trabecular bone were significantly, independently, and inversely associated with the Mental Development Index (MDI) scores of the Bayley Scale. In relation to the lowest quartile of trabecular bone lead, the second, third, and fourth quartiles were associated with 5.4-, 7.2-, and 6.5-point decrements in adjusted MDI scores. A 2-fold increase in cord blood lead level (eg, from 5 to 10 micro g/dL) was associated with a 3.1-point decrement in MDI score, which is comparable to the magnitude of effect seen in previous studies. CONCLUSION Higher maternal trabecular bone lead levels constitute an independent risk factor for impaired mental development in infants at 24 months of age. This effect is probably attributable to mobilization of maternal bone lead stores, a phenomenon that may constitute a significant public health problem in view of the long residence time of lead in bone.

[1]  Howard Hu,et al.  Calcium supplements and bone resorption in pregnancy: a randomized crossover trial. , 2003, American journal of preventive medicine.

[2]  Howard Hu,et al.  Effect of Maternal Bone Lead on Length and Head Circumference of Newborns and 1-Month-Old Infants , 2002, Archives of environmental health.

[3]  I. Romieu,et al.  Effect of maternal lead burden on infant weight and weight gain at one month of age among breastfed infants. , 2001, Pediatrics.

[4]  A. Todd,et al.  Maternal bone lead contribution to blood lead during and after pregnancy. , 2000, Environmental research.

[5]  C. Amarasiriwardena,et al.  Validation of K x-ray fluorescence bone lead measurements by inductively coupled plasma mass spectrometry in cadaver legs. , 2000, Medical physics.

[6]  Chonghuai Yan,et al.  Low-level prenatal lead exposure and neurobehavioral development of children in the first year of life: a prospective study in Shanghai. , 1998, Environmental research.

[7]  Howard Hu,et al.  Bone lead as a biological marker in epidemiologic studies of chronic toxicity: conceptual paradigms. , 1998, Environmental health perspectives.

[8]  R. Smith,et al.  Osteoporosis during pregnancy and its management. , 1998, Scandinavian journal of rheumatology. Supplement.

[9]  M. Mendelsohn,et al.  Biomarkers: Medical and Workplace Applications , 1998 .

[10]  Howard Hu,et al.  Decrease in birth weight in relation to maternal bone-lead burden. , 1997, Pediatrics.

[11]  B. Specker,et al.  The effect of calcium supplementation on bone density during lactation and after weaning. , 1997, The New England journal of medicine.

[12]  G. Vimpani,et al.  Pregnancy increases mobilization of lead from maternal skeleton. , 1997, The Journal of laboratory and clinical medicine.

[13]  R. Goyer.  Results of lead research: prenatal exposure and neurological consequences. , 1996, Environmental health perspectives.

[14]  M. Sowers.  Pregnancy and lactation as risk factors for subsequent bone loss and osteoporosis , 1996, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[15]  Howard Hu,et al.  Levels of lead in blood and bone of women giving birth in a Boston hospital. , 1996, Archives of environmental health.

[16]  D. Bellinger.  Interpreting the literature on lead and child development: the neglected role of the "experimental system". , 1995, Neurotoxicology and teratology.

[17]  A. Todd,et al.  Improvements in the calibration of 109Cd K x-ray fluorescence systems for measuring bone lead in vivo. , 1994, Physics in medicine and biology.

[18]  A. Rotnitzky,et al.  The relationship between bone lead and hemoglobin. , 1994, JAMA.

[19]  P. Shrout,et al.  Consequences of lead exposure and iron supplementation on childhood development at age 4 years. , 1994, Neurotoxicology and teratology.

[20]  J Schwartz,et al.  Low-level lead exposure and children's IQ: a meta-analysis and search for a threshold. , 1994, Environmental research.

[21]  P. Shrout,et al.  Independent effects of lead exposure and iron deficiency anemia on developmental outcome at age 2 years. , 1992, The Journal of pediatrics.

[22]  G. Vimpani,et al.  Environmental exposure to lead and children's intelligence at the age of seven years. The Port Pirie Cohort Study. , 1992, The New England journal of medicine.

[23]  H. Hu,et al.  The use of K X-ray fluorescence for measuring lead burden in epidemiological studies: high and low lead burdens and measurement uncertainty. , 1991, Environmental health perspectives.

[24]  G. Vimpani,et al.  Lead in the placenta, membranes, and umbilical cord in relation to pregnancy outcome in a lead-smelter community. , 1991, Environmental health perspectives.

[25]  P. Succop,et al.  Lead exposure and neurobehavioral development in later infancy. , 1990, Environmental health perspectives.

[26]  D. Svendsgaard,et al.  Neurobehavioral deficits after low level lead exposure in neonates: the Mexico City pilot study. , 1989, Neurotoxicology and teratology.

[27]  G. Vimpani,et al.  Port Pirie Cohort study: childhood blood lead and neuropsychological development at age two years. , 1988, Journal of epidemiology and community health.

[28]  M. Marler,et al.  Low level lead exposure in the prenatal and early preschool periods: early preschool development. , 1987, Neurotoxicology and teratology.

[29]  C Waternaux,et al.  Longitudinal analyses of prenatal and postnatal lead exposure and early cognitive development. , 1987, The New England journal of medicine.

[30]  A. Kauppila,et al.  Lead and cadmium concentrations in maternal and umbilical cord blood, amniotic fluid, placenta, and amniotic membranes. , 1986, American journal of obstetrics and gynecology.