title: Fetal lead exposure at each stage of pregnancy as a predictor of infant mental development.
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 microg/dL and 14% of values >or=10 microg/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.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA. howardhu@umich.edu
authors.forename: Howard
authors.initials: H
authors.lastname: Hu
authors.forename: Martha María
authors.initials: MM
authors.lastname: Téllez-Rojo
authors.forename: David
authors.initials: D
authors.lastname: Bellinger
authors.forename: Donald
authors.initials: D
authors.lastname: Smith
authors.forename: Adrienne S
authors.initials: AS
authors.lastname: Ettinger
authors.forename: Héctor
authors.initials: H
authors.lastname: Lamadrid-Figueroa
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.forename: Lourdes
authors.initials: L
authors.lastname: Schnaas
authors.forename: Adriana
authors.initials: A
authors.lastname: Mercado-García
authors.forename: Mauricio
authors.initials: M
authors.lastname: Hernández-Avila
mesh_terms: D000293:Adolescent; D000328:Adult; D002657:Child Development / Q000187:drug effects*; D002675:Child, Preschool; D004785:Environmental Pollutants / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D006801:Humans; D007223:Infant; D007854:Lead / Q000097:blood*; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects*; D008800:Mexico; D011247:Pregnancy; D011264:Pregnancy Trimesters / Q000097:blood; D011297:Prenatal Exposure Delayed Effects; D011581:Psychological Tests
chemical_list: D004785:Environmental Pollutants; D007854:Lead