| Fetal Lead Exposure at Each Stage of Pregnancy as a Predictor of Infant Mental Development Howard Hu,1,2 Martha María Téllez-Rojo,3 David Bellinger,1,4 Donald Smith,5 Adrienne S. Ettinger,1,2 Héctor Lamadrid-Figueroa,3 Joel Schwartz,1,2 Lourdes Schnaas,6 Adriana Mercado-García,3 and Mauricio Hernández-Avila3 1Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA; 2Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA; 3Centro de Investigación en Salud Poblacional, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México; 4Department of Neurology, Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA; 5Department of Biology and Environmental Toxicology, University of California at Santa Cruz, Santa Cruz, California, USA; 6Instituto Nacional de Perinatologia, Mexico City, Mexico Abstract
Background: The impact of prenatal lead exposure on neurodevelopment remains unclear in terms of consistency, the trimester of greatest vulnerability, and the best method for estimating fetal lead exposure. Objective: We studied prenatal lead exposure's impact on neurodevelopment using repeated measures of fetal dose as reflected by maternal whole blood and plasma lead levels. Methods: We measured lead in maternal plasma and whole blood during each trimester in 146 pregnant women in Mexico City. We then measured umbilical cord blood lead at delivery and, when offspring were 12 and 24 months of age, measured blood lead and administered the Bayley Scales of Infant Development. We used multivariate regression, adjusting for covariates and 24-month blood lead, to compare the impacts of our pregnancy measures of fetal lead dose. Results: Maternal lead levels were moderately high with a first-trimester blood lead mean (± SD) value of 7.1 ± 5.1 µg/dL and 14% of values ≥10 µg/dL. Both maternal plasma and whole blood lead during the first trimester (but not in the second or third trimester) were significant predictors (p < 0.05) of poorer Mental Development Index (MDI) scores. In models combining all three trimester measures and using standardized coefficients, the effect of first-trimester maternal plasma lead was somewhat greater than the effect of first-trimester maternal whole blood lead and substantially greater than the effects of second- or third-trimester plasma lead, and values averaged over all three trimesters. A 1-SD change in first-trimester plasma lead was associated with a reduction in MDI score of 3.5 points. Postnatal blood lead levels in the offspring were less strongly correlated with MDI scores. Conclusions: Fetal lead exposure has an adverse effect on neurodevelopment, with an effect that may be most pronounced during the first trimester and best captured by measuring lead in either maternal plasma or whole blood. Key words: bone, IQ, lead, plasma, pregnancy, neurodevelopment. Environ Health Perspect 114: 1730–1735 (2006) . doi:10.1289/ehp.9067 available via http://dx.doi.org/ [Online 19 July 2006]
Address correspondence to H. Hu, Department of Environmental Health Sciences, Building 1, Room 6667, University of Michigan School of Public Health, Ann Arbor, MI 48109-2029 USA. Telephone: (734) 764-3188. Fax: (734) 734.936-7283. E-mail: howardhu@umich.edu This study was supported by National Institute of Environmental Health Sciences (NIEHS) grants P42-ES05947, R01-ES07821, Center Grant P30-ES 00002, and T32-ES07069, and by Consejo Nacional de Ciencia y Tecnología (CONACyT) Grant 4150M9405 and CONSERVA, Department of Federal District, México. Additional support for the interpretation of results and authorship of this publication was made possible by NIEHS P01 ES012874, and a STAR Research Assistance Agreement RD-83172501 awarded by the U.S. Environmental Protection Agency (EPA) . The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, National Institutes of Health, or the U.S. EPA. The authors declare they have no competing financial interests. Received 2 February 2006 ; accepted 19 July 2006.
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