title: Maternal blood manganese levels and infant birth weight.
abstract: BACKGROUND
  Manganese is both an essential element and a known neurotoxicant to children. High manganese exposures have been associated with negative reproductive outcomes in animals, but few epidemiologic studies have examined the effects of human fetal manganese exposure.
  
  
  METHODS
  We studied the association between maternal and umbilical cord blood manganese levels and birth weight in a cohort of 470 mother-infant pairs born at term (>or=37 weeks gestation) in Ottawa County, Oklahoma. Nonlinear spline and quadratic regression models were used to test the hypothesis of an inverted U-shaped relationship between manganese levels and birth weight.
  
  
  RESULTS
  Mean (standard deviation) concentration of manganese was 2.4 (0.95) microg/dL in the maternal blood and 4.2 (1.6) microg/dL in the cord blood. Umbilical cord manganese was not associated with birth weight. A nonlinear relationship was observed between maternal manganese and birth weight after adjusting for potential confounders. Birth weight increased with manganese levels up to 3.1 microg/L, and then a slight reduction in weight was observed at higher levels. Compared with the 3.1-microg/L point of inflection, birth weight estimates at the 5th (1.3 microg/L) and 95th (4.0 microg/L) percentiles of exposure were -160 g (95% confidence interval = -286 to -33) and -46 g (-38 to 131), respectively.
  
  
  CONCLUSIONS
  Maternal blood manganese levels during pregnancy are associated with birth weight in a nonlinear pattern in full-term infants. These findings suggest that manganese may affect fetal growth. Possible detrimental effects of elevated manganese levels on the fetus should be further examined in more highly exposed populations.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. zota@silentspring.org
authors.forename: Ami R
authors.initials: AR
authors.lastname: Zota
authors.forename: Adrienne S
authors.initials: AS
authors.lastname: Ettinger
authors.forename: Maryse
authors.initials: M
authors.lastname: Bouchard
authors.forename: Chitra J
authors.initials: CJ
authors.lastname: Amarasiriwardena
authors.forename: Joel
authors.initials: J
authors.lastname: Schwartz
authors.forename: Howard
authors.initials: H
authors.lastname: Hu
authors.forename: Robert O
authors.initials: RO
authors.lastname: Wright
mesh_terms: D000293:Adolescent; D000328:Adult; D001724:Birth Weight / Q000187:drug effects*; D003430:Cross-Sectional Studies; D005260:Female; D005312:Fetal Blood; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008345:Manganese / Q000009:adverse effects / Q000097:blood*; D015233:Models, Statistical; D009035:Mothers; D009825:Oklahoma; D055815:Young Adult
chemical_list: D008345:Manganese