title: Maternal smoking and adverse birth outcomes among singletons and twins.
abstract: OBJECTIVE
  This study assessed the effects of maternal smoking on birth outcomes among singletons and twins.
  
  
  METHODS
  An algorithm was developed to link twins with their siblings in the 1995 Perinatal Mortality Data Set. A random-effects logistic regression model was then used to estimate the association between maternal smoking and several adverse outcomes for a random sample of singletons and for all twins with available maternal smoking information.
  
  
  RESULTS
  The algorithm successfully linked sibling pairs for 91% of the twin sample. Maternal smoking was associated with a significantly increased risk of low birthweight, very low birthweight, and gestation of less than 33 weeks for both singletons and twins and with an increased risk of gestation of less than 38 weeks, infant mortality, and placental abruption for singletons. Among smokers, negative impacts on the risk of low birthweight, very low birthweight, and extreme premature delivery were significantly higher for women carrying twins.
  
  
  CONCLUSIONS
  Some of the negative effects of smoking on low birthweight and preterm delivery are greater for twins than for singletons. Women carrying twins should be warned that smoking increases their already high risk of serious infant health problems.
authors.affiliation: Department of Health Management and Policy, University of Michigan School of Public Health, Ann Arbor 48109-2029, USA. haroldp@umich.edu
authors.forename: H
authors.initials: H
authors.lastname: Pollack
authors.forename: P M
authors.initials: PM
authors.lastname: Lantz
authors.forename: J G
authors.initials: JG
authors.lastname: Frohna
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D001724:Birth Weight; D005260:Female; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D008297:Male; D011247:Pregnancy; D011248:Pregnancy Complications; D011256:Pregnancy Outcome; D015995:Prevalence; D012306:Risk; D012907:Smoking / Q000009:adverse effects*; D014427:Twins / Q000706:statistics & numerical data*