title: Does multiple gestation impact birthweight deficit from smoking?
abstract: OBJECTIVE
  To test the hypothesis that the combined birthweight deficit from smoking in twin gestation is significantly greater than previously described for singletons.
  
  
  METHODS
  Retrospective cohort study of White/Black live-born twins, 32 to 40 weeks of gestation, 1990 to 2005, Kansas City, MO. Data were analyzed by t-test, χ(2), linear and linear regression analyses.
  
  
  RESULTS
  The cohort comprised 1190 twin pairs, 58% Whites and 55% ≥37 weeks. Smoking rate was 14.5% and similar by race (14.2% White vs 14.8%, P=0.772). The aggregate birthweight of twins of nonsmokers was greater, 5116 g ± 25 g vs 4870 g ± 59 g, P<0.001 (mean±s.d.) and the difference was 264 g (95% confidence interval, 156 to 372 g) after adjusting for other variables in linear regression analyses.
  
  
  CONCLUSIONS
  Smoking-associated growth restriction in twins is quantitatively similar to that of singletons. This finding is suggestive of dissipation or a ceiling effect to the growth-restricting effect of cigarette smoking.
authors: Department of Pediatrics, Children's Mercy Hospitals and Clinics/University of Missouri Kansas City School of Medicine, Kansas City, MO, USA.
authors: F A
authors: FA
authors: Okah
authors: Department of Pediatrics, Children's Mercy Hospitals and Clinics/University of Missouri Kansas City School of Medicine, Kansas City, MO, USA.
authors: A A
authors: AA
authors: Oshodi
authors: University of Missouri Kansas City School of Pharmacy, Kansas City, MO, USA.
authors: Y
authors: Y
authors: Liu
authors: Office of Epidemiology and Community Health Monitoring, Health Department, Kansas City, MO, USA.
authors: J
authors: J
authors: Cai
mesh_terms: D000328:Adult; D001724:Birth Weight; D005260:Female; D005317:Fetal Growth Retardation / Q000209:etiology; D006801:Humans; D007231:Infant, Newborn; D016014:Linear Models; D008297:Male; D011247:Pregnancy; D059285:Pregnancy, Twin; D012189:Retrospective Studies; D012907:Smoking / Q000009:adverse effects*; D055815:Young Adult