title: Cord Blood Methylmercury and Fetal Growth Outcomes in Baltimore Newborns: Potential Confounding and Effect Modification by Omega-3 Fatty Acids, Selenium, and Sex.
abstract: BACKGROUND
  Methylmercury (MeHg) may affect fetal growth; however, prior research often lacked assessment of mercury speciation, confounders, and interactions.
  
  
  OBJECTIVE
  Our objective was to assess the relationship between MeHg and fetal growth as well as the potential for confounding or interaction of this relationship from speciated mercury, fatty acids, selenium, and sex.
  
  
  METHODS
  This cross-sectional study includes 271 singletons born in Baltimore, Maryland, 2004-2005. Umbilical cord blood was analyzed for speciated mercury, serum omega-3 highly unsaturated fatty acids (n-3 HUFAs), and selenium. Multivariable linear regression models controlled for gestational age, birth weight, maternal age, parity, prepregnancy body mass index, smoking, hypertension, diabetes, selenium, n-3 HUFAs, and inorganic mercury (IHg).
  
  
  RESULTS
  Geometric mean cord blood MeHg was 0.94 μg/L (95% CI: 0.84, 1.07). In adjusted models for ponderal index, βln(MeHg) = -0.045 (g/cm(3)) × 100 (95% CI: -0.084, -0.005). There was no evidence of a MeHg × sex interaction with ponderal index. Contrastingly, there was evidence of a MeHg × n-3 HUFAs interaction with birth length [among low n-3 HUFAs, βln(MeHg) = 0.40 cm, 95% CI: -0.02, 0.81; among high n-3 HUFAs, βln(MeHg) = -0.15, 95% CI: -0.54, 0.25; p-interaction = 0.048] and head circumference [among low n-3 HUFAs, βln(MeHg) = 0.01 cm, 95% CI: -0.27, 0.29; among high n-3 HUFAs, βln(MeHg) = -0.37, 95% CI: -0.63, -0.10; p-interaction = 0.042]. The association of MeHg with birth weight and ponderal index was affected by n-3 HUFAs, selenium, and IHg. For birth weight, βln(MeHg) without these variables was -16.8 g (95% CI: -75.0, 41.3) versus -29.7 (95% CI: -93.9, 34.6) with all covariates. Corresponding values for ponderal index were -0.030 (g/cm(3)) × 100 (95% CI: -0.065, 0.005) and -0.045 (95% CI: -0.084, -0005).
  
  
  CONCLUSIONS
  We observed an association of increased MeHg with decreased ponderal index. There is evidence for interaction between MeHg and n-3 HUFAs; infants with higher MeHg and n-3 HUFAs had lower birth length and head circumference. These results should be verified with additional studies.
authors.affiliation: School of Health Sciences, Purdue University, West Lafayette, Indiana, USA.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Wells
authors.forename: Julie B
authors.initials: JB
authors.lastname: Herbstman
authors.forename: Yu Hong
authors.initials: YH
authors.lastname: Lin
authors.forename: Jeffery
authors.initials: J
authors.lastname: Jarrett
authors.forename: Carl P
authors.initials: CP
authors.lastname: Verdon
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ward
authors.forename: Kathleen L
authors.initials: KL
authors.lastname: Caldwell
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Hibbeln
authors.forename: Frank R
authors.initials: FR
authors.lastname: Witter
authors.forename: Rolf U
authors.initials: RU
authors.lastname: Halden
authors.forename: Lynn R
authors.initials: LR
authors.lastname: Goldman
mesh_terms: D015142:Baltimore; D001724:Birth Weight / Q000187:drug effects; D049628:Body Size / Q000187:drug effects; D002508:Cephalometry; D003430:Cross-Sectional Studies; D015525:Fatty Acids, Omega-3 / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D047109:Fetal Development / Q000187:drug effects*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008767:Methylmercury Compounds / Q000097:blood*; D011247:Pregnancy; D012643:Selenium / Q000097:blood*; D012737:Sex Factors
chemical_list: D015525:Fatty Acids, Omega-3; D008767:Methylmercury Compounds; D012643:Selenium