title: Variability of urinary phthalate metabolite and bisphenol A concentrations before and during pregnancy.
abstract: BACKGROUND
  Gestational phthalate and bisphenol A (BPA) exposure may increase the risk of adverse maternal/child health outcomes, but there are few data on the variability of urinary biomarkers before and during pregnancy.
  
  
  OBJECTIVE
  We characterized the variability of urinary phthalate metabolite and BPA concentrations before and during pregnancy and the ability of a single spot urine sample to classify average gestational exposure.
  
  
  METHODS
  We collected 1,001 urine samples before and during pregnancy from 137 women who were partners in couples attending a Boston fertility clinic and who had a live birth. Women provided spot urine samples before (n ≥ 2) and during (n ≥ 2) pregnancy. We measured urinary concentrations of monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-iso-butyl phthalate, monobenzyl phthalate (MBzP), four metabolites of di-(2-ethylhexyl) phthalate (DEHP), and BPA. After adjusting for specific gravity, we characterized biomarker variability using intraclass correlation coefficients (ICCs) and conducted several surrogate category analyses to determine whether a single spot urine sample could adequately classify average gestational exposure.
  
  
  RESULTS
  Absolute concentrations of phthalate metabolites and BPA were similar before and during pregnancy. Variability was higher during pregnancy than before pregnancy for BPA and MBzP, but similar during and before pregnancy for MBP, MEP, and ΣDEHP. During pregnancy, MEP (ICC = 0.50) and MBP (ICC = 0.45) were less variable than BPA (ICC = 0.12), MBzP (ICC = 0.25), and ΣDEHP metabolites (ICC = 0.08). Surrogate analyses suggested that a single spot urine sample may reasonably classify MEP and MBP concentrations during pregnancy, but more than one sample may be necessary for MBzP, DEHP, and BPA.
  
  
  CONCLUSIONS
  Urinary phthalate metabolites and BPA concentrations were variable before and during pregnancy, but the magnitude of variability was biomarker specific. A single spot urine sample adequately classified MBP and MEP concentrations during pregnancy. The present results may be related to unique features of the women studied, and replication in other pregnancy cohorts is recommended.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA.
authors.forename: Joe M
authors.initials: JM
authors.lastname: Braun
authors.forename: Kristen W
authors.initials: KW
authors.lastname: Smith
authors.forename: Paige L
authors.initials: PL
authors.lastname: Williams
authors.forename: Antonia M
authors.initials: AM
authors.lastname: Calafat
authors.forename: Katharine
authors.initials: K
authors.lastname: Berry
authors.forename: Shelley
authors.initials: S
authors.lastname: Ehrlich
authors.forename: Russ
authors.initials: R
authors.lastname: Hauser
mesh_terms: D000293:Adolescent; D000328:Adult; D001559:Benzhydryl Compounds; D001900:Boston; D005260:Female; D006801:Humans; D008875:Middle Aged; D010636:Phenols / Q000097:blood*; D010795:Phthalic Acids / Q000652:urine*; D011247:Pregnancy; D055815:Young Adult; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D010636:Phenols; D010795:Phthalic Acids; C006780:bisphenol A; D000098826:Bisphenol A Compounds