title: Cotinine Validation of Self-Reported Smoking During Pregnancy in the Swedish Medical Birth Register.
abstract: BACKGROUND
  Self-reported data on smoking during pregnancy from the Medical Birth Register of Sweden (MBR) are widely used. However, underreporting of such behavior may occur, leading to biases. It is of importance to validate the smoking data in the MBR. The main objective was to investigate the agreement between self-reported smoking data from the MBR and cotinine levels in maternal serum among women from the general population in the region of Skåne, Sweden. We also estimated the transfer of cotinine from mother to fetus.
  
  
  METHODS
  From a cohort used previously to investigate the relationship between intrauterine environmental exposures and offspring neuropsychiatric outcomes, there were 204 control children retrieved from the MBR with data on maternal smoking in early pregnancy registered. Data on maternal and umbilical cord cotinine at delivery were available for these children from a regional biobank.
  
  
  RESULTS
  There was a high agreement between cotinine levels and MBR smoking data (κ = 0.82) and a high correlation between cotinine levels in maternal and umbilical cord serum (r s = 0.90, P < .001). Of the self-reported nonsmokers, 95% (95% confidence interval: 89% to 97%) were classified as nonsmokers after cotinine measurements.
  
  
  CONCLUSIONS
  In these data, we found that the agreement between mothers' self-reported smoking habits during pregnancy and their levels of serum cotinine was high, as was the transfer of cotinine from mother to fetus. This indicates that birth register data on pregnancy smoking in Sweden could be considered a valid measure.
authors.affiliation: Division of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, Lund, Sweden; kristina.mattsson@med.lu.se.
authors.forename: Kristina
authors.initials: K
authors.lastname: Mattsson
authors.affiliation: Division of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, Lund, Sweden;
authors.forename: Karin
authors.initials: K
authors.lastname: Källén
authors.affiliation: Division of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, Lund, Sweden;
authors.forename: Anna
authors.initials: A
authors.lastname: Rignell-Hydbom
authors.affiliation: Division of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, Lund, Sweden;
authors.forename: Christian H
authors.initials: CH
authors.lastname: Lindh
authors.affiliation: Division of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, Lund, Sweden;
authors.forename: Bo A G
authors.initials: BA
authors.lastname: Jönsson
authors.affiliation: Department of Child and Adolescent Psychiatry, Institution of Clinical Sciences, Lund University, Lund, Sweden;
authors.forename: Peik
authors.initials: P
authors.lastname: Gustafsson
authors.affiliation: Department of Obstetrics and Gynecology, Institution of Clinical Sciences, Skåne University Hospital, Lund University, Malmö, Sweden;
authors.forename: Per
authors.initials: P
authors.lastname: Olofsson
authors.affiliation: Department of Clinical Sciences, Unit of Pediatric Endocrinology, Lund University/Clinical Research Centre, Malmö, Sweden.
authors.forename: Sten A
authors.initials: SA
authors.lastname: Ivarsson
authors.affiliation: Division of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, Lund, Sweden;
authors.forename: Lars
authors.initials: L
authors.lastname: Rylander
mesh_terms: D000328:Adult; D003367:Cotinine / Q000097:blood*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D006801:Humans; D008431:Maternal-Fetal Exchange; D011247:Pregnancy / Q000097:blood* / Q000523:psychology; D011297:Prenatal Exposure Delayed Effects; D015995:Prevalence; D012042:Registries; D057566:Self Report; D012907:Smoking / Q000097:blood / Q000453:epidemiology*; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult
chemical_list: D003367:Cotinine