title: Relationships between cigarette smoking during pregnancy, gestational age, maternal weight gain, and infant birthweight.
abstract: OBJECTIVE
  To estimate the effect of smoking on infant birthweight independent of gestational age and maternal weight gain during pregnancy.
  
  
  METHODS
  Stepwise regression was used to identify sets of maternal and infant characteristics not modified by prenatal smoking that were predictors of infant birthweight, gestational age, and net maternal weight gain. These were then included in regression analyses to assess the effects of smoking, as measured by cigarette consumption, exhaled carbon monoxide, or urinary cotinine on gestational age, net maternal weight gain, and infant birthweight.
  
  
  RESULTS
  After adjustment for nonmodifiable factors, smoking accounted for 1.5-3.1% of the variance in gestational age at delivery. It accounted for 5.3-7.7% of the variance in net maternal weight gain after adjustment for nonmodifiable factors and gestational age. After adjustment for gestational age and net maternal weight gain, and the nonmodifiable factors, smoking accounted for 2.7-5.2% of the variance in infant birthweight.
  
  
  CONCLUSIONS
  Most of the gain in infant birthweight on quitting smoking is due to the independent effect of smoking on fetal growth restriction, with much smaller gains related to increased maternal weight gain and a slightly longer gestational age.
authors.affiliation: Office of Health Promotion Research (RHS-W), University of Vermont, Burlington, VT, USA. rseckerw@zoo.uvm.edu
authors.forename: Roger H
authors.initials: RH
authors.lastname: Secker-Walker
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Vacek
mesh_terms: D000328:Adult; D001724:Birth Weight; D001944:Breath Tests; D002248:Carbon Monoxide / Q000378:metabolism; D003367:Cotinine / Q000652:urine; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy / Q000502:physiology*; D011297:Prenatal Exposure Delayed Effects; D012044:Regression Analysis; D012907:Smoking / Q000503:physiopathology* / Q000652:urine; D015430:Weight Gain
chemical_list: D002248:Carbon Monoxide; D003367:Cotinine