title: The effect of smoking on pre-eclampsia in twin pregnancy.
abstract: OBJECTIVE
  To assess the effect of smoking on the incidence of pre-eclampsia and on perinatal outcome in twin pregnancy.
  
  
  METHODS
  Retrospective study using Aberdeen Maternity and Neonatal Databank.
  
  
  METHODS
  Grampian, Orkney and Shetland.
  
  
  METHODS
  All 1,575 twin pregnancies delivered in the years 1969-1971 and 1976-1997 (when smoking data were available).
  
  
  METHODS
  In all twin pregnancies the effects of smoking on pre-eclampsia were analysed by parity and gestation at delivery. The effect of smoking upon late miscarriage and perinatal outcome was analysed without subdivision.
  
  
  METHODS
  Pre-eclampsia and perinatal outcome.
  
  
  RESULTS
  Primiparae had significantly higher rates of pre-eclampsia than multiparae and were delivered significantly earlier. The incidence of pre-eclampsia in smokers was significantly lower only in multiparae. Length of gestation was significantly shorter in multiparous smokers. The effect of smoking on pre-eclampsia appeared to be direct in multiparae but possibly indirect in primiparae (by causing earlier delivery). Smokers had a higher late miscarriage rate than nonsmokers.
  
  
  CONCLUSIONS
  In twin pregnancy the apparent protective effect of smoking against pre-eclampsia is significant only in multiparae, suggesting that in primiparae the smoking effect is overwhelmed by the other reasons for the development of pre-eclampsia. Smoking in twin pregnancy is not recommended due to the worse fetal outcome rates.
authors.affiliation: Department of Obstetrics and Gynaecology, University of Aberdeen, UK.
authors.forename: C L
authors.initials: CL
authors.lastname: Martin
authors.forename: M H
authors.initials: MH
authors.lastname: Hall
authors.forename: D M
authors.initials: DM
authors.lastname: Campbell
mesh_terms: D005260:Female; D006801:Humans; D015994:Incidence; D010298:Parity; D011225:Pre-Eclampsia / Q000453:epidemiology* / Q000209:etiology; D011247:Pregnancy; D011256:Pregnancy Outcome; D011272:Pregnancy, Multiple; D012189:Retrospective Studies; D012606:Scotland / Q000453:epidemiology; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*