title: Fetal exposure to secondhand tobacco smoke assessed by maternal self-reports and cord blood cotinine: prospective cohort study in Krakow.
abstract: OBJECTIVE
  While the validity of self-reported smoking habits is generally judged as satisfactory, objective markers of secondhand smoke (SHS) exposure may be more useful in validating the causal links between prenatal SHS and health effects. The cohort study in Krakow provided an opportunity for comparative assessment of fetal exposure to SHS based upon questionnaires and cord blood cotinine measurements.
  
  
  METHODS
  The study sample included 467 newborns born to women recruited in the first and second trimester of pregnancy. To compare the validity of self-reported SHS and cord blood cotinine levels in assessing the association between fetal passive smoking and health effects of newborns, we separately examined the regression coefficients of birthweight on self-reported number of cigarettes smoked by other household members during the entire pregnancy and cord blood cotinine levels.
  
  
  RESULTS
  In the non-exposed newborns the geometric mean of cord blood cotinine was 0.077 ng/ml and was significantly lower than in newborns with a maternal report of SHS. Cord cotinine levels were more highly correlated with a self-reported number of cigarettes smoked daily at home in the third trimester of pregnancy. The two measures of SHS (number of cigarettes and number of hours of daily exposure) were equally well correlated with cord blood cotinine levels. Using cotinine as the exposure variable, overall the association was not significant; but among the subgroup with cord cotinine levels above the median (> or =0.083 ng/ml), the association with birthweight was significant (beta coefficient = -113.65, P = 0.041).
  
  
  CONCLUSIONS
  The study provides evidence that the assessment of fetal SHS exposure based on cord blood cotinine produced better estimates of the association between exposure and birth outcomes.
authors.affiliation: Department of Epidemiology and Preventive Medicine, College of Medicine, Jagiellonian University, 7, Kopernika street, Krakow, Poland. myjedryc@cyf-kr.edu.pl
authors.forename: Wieslaw
authors.initials: W
authors.lastname: Jedrychowski
authors.forename: Frederica
authors.initials: F
authors.lastname: Perera
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Mroz
authors.forename: Susan
authors.initials: S
authors.lastname: Edwards
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Flak
authors.forename: John T
authors.initials: JT
authors.lastname: Bernert
authors.forename: Dorota
authors.initials: D
authors.lastname: Mrozek-Budzyn
authors.forename: Agata
authors.initials: A
authors.lastname: Sowa
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Musiał
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003367:Cotinine / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D005333:Fetus; D006801:Humans; D018811:Maternal Exposure; D011044:Poland; D011247:Pregnancy; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D014028:Tobacco Smoke Pollution; D055815:Young Adult
chemical_list: D014028:Tobacco Smoke Pollution; D003367:Cotinine