title: Use of meconium in perinatal epidemiology: potential benefits and pitfalls.
abstract: OBJECTIVE
  Meconium is a biomarker matrix that can be used to assess cumulative exposures in epidemiologic studies of prenatal risk factors. Depending on when meconium is collected, different exposure windows during pregnancy can be measured. However, little guidance exists regarding the extent to which timing of meconium collection will influence resulting effect estimates.
  
  
  METHODS
  We performed a simulation study of prenatal tobacco smoke exposure (assessed from meconium nicotine) and birth weight. We discuss four typical meconium collection methods capturing different exposure windows and assess the biases induced by these methods.
  
  
  RESULTS
  In simulations assuming that exposure to tobacco smoke only during late gestation was of etiologic relevance to birth weight, use of a meconium collection method that captured exposure windows other than late gestation resulted in biased estimates of the true nicotine-birth weight association.
  
  
  CONCLUSIONS
  Using meconium collection methods that do not reflect an exposure window of etiologic relevance can lead to biased results and erroneous conclusions regarding the nature of prenatal exposure-outcome associations. Understanding how prenatal exposure patterns vary across the pregnancy and exposure windows of etiologic relevance is essential in determining when and how to collect meconium for use in biomarker studies of prenatal exposure.
authors.affiliation: Department of Epidemiology and Biostatistics, Drexel University School of Public Health, Philadelphia, PA. Electronic address: byp24@drexel.edu.
authors.forename: Bo Y
authors.initials: BY
authors.lastname: Park
authors.affiliation: Department of Epidemiology and Biostatistics, Drexel University School of Public Health, Philadelphia, PA.
authors.forename: Brian K
authors.initials: BK
authors.lastname: Lee
mesh_terms: D015415:Biomarkers / Q000032:analysis / Q000097:blood; D001724:Birth Weight; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D018811:Maternal Exposure; D008470:Meconium / Q000737:chemistry* / Q000378:metabolism; D009538:Nicotine / Q000097:blood / Q000378:metabolism*; D011247:Pregnancy; D011264:Pregnancy Trimesters; D011297:Prenatal Exposure Delayed Effects; D012907:Smoking / Q000009:adverse effects / Q000378:metabolism*; D013997:Time Factors; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D015415:Biomarkers; D014028:Tobacco Smoke Pollution; D009538:Nicotine
keywords: Epidemiology; Exposure assessment; Low birth weight; Meconium; Nicotine; Smoking